Downhole Acoustic Emission Formation Sampling

ABSTRACT

A method, system and apparatus for testing properties of a rock formation surrounding a wellbore in situ. The apparatus includes a tool body, one or more indenters, and one or more acoustic sensors. The body includes an outer surface that defines one or more cavities therein. Each cavity extends into the body. Each indenter is positioned within a corresponding cavity and is positionable into an operating position and a non-operating position. The acoustic sensor is positioned within the cavity and adjacent to the indenter. The indenter is positioned at least partially beyond the outer surface when in the operating position. The acoustic sensor senses one or more acoustic events occurring when the indenter is in the operating position. The apparatus is inserted into the wellbore. Once inserted, the indenter applies a load onto the rock formation causing cracking and the sensor receives the generated acoustic transmissions. The transmissions are analyzed.

RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 13/152,126, entitled “Acoustic Emission ToughnessTesting Having Smaller Noise Ratio” and filed on Jun. 2, 2011, which isa continuation-in-part of U.S. patent application Ser. No. 12/963,913,entitled “Acoustic Emission Toughness Testing For PDC, PCBN, Or OtherHard Or Superhard Materials” and filed on Dec. 9, 2010, which is acontinuation-in-part of U.S. patent application Ser. No. 12/769,221,entitled “Acoustic Emission Toughness Testing For PDC, PCBN, Or OtherHard Or Superhard Materials” and filed on Apr. 28, 2010, which is acontinuation-in-part of U.S. patent application Ser. No. 12/754,784,entitled “Acoustic Emission Toughness Testing For PDC, PCBN, Or OtherHard Or Superhard Material Inserts” and filed on Apr. 6, 2010, which areall hereby incorporated by reference.

The present application also is related to U.S. patent application Ser.No. 12/754,738, entitled “Acoustic Emission Toughness Testing For PDC,PCBN, Or Other Hard Or Superhard Material Inserts” and filed on Apr. 6,2010, which also is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to a method and apparatus fortesting one or more rock properties; and more particularly, to a methodand apparatus for testing, in situ, one or more properties, such ascompressive strength, of rock formations found within a wellbore usingacoustic emissions.

BACKGROUND

FIG. 1 shows a superhard material 100 that is insertable within adownhole tool (not shown), such as a drill bit or a reamer, inaccordance with an exemplary embodiment of the invention. One example ofa superhard material 100 is a cutting element 100, or cutter or insert,for rock bits, as shown in FIG. 1. However, the superhard material 100can be formed into other structures based upon the application that itis to be used in. In other examples, the superhard material 100 is arock sample, which can be obtained from within a wellbore or from othersources. The cutting element 100 typically includes a substrate 110having a contact face 115 and a cutting table 120. The cutting table 120is fabricated using an ultra hard layer which is bonded to the contactface 115 by a sintering process according to one example. According tosome examples, the substrate 110 is generally made from tungstencarbide-cobalt, or tungsten carbide, while the cutting table 120 isformed using a polycrystalline ultra hard material layer, such aspolycrystalline diamond (“PCD”) or polycrystalline cubic boron nitride(“PCBN”). These cutting elements 100 are fabricated according toprocesses and materials known to persons having ordinary skill in theart. Although the cutting table 120 is shown having a substantiallyplanar outer surface, the cutting table 120 can have alternative shapedouter surfaces, such as dome-shaped, concave-shaped, or other non-planarshaped outer surfaces, in other embodiments. Although some exemplaryformulations for the cutting element 100 have been provided, otherformulations and structures known to people having ordinary skill in theart can be used depending upon the application. Although rock drillingis one application that the superhard material 100 can be used in orobtained from and which is described hereinbelow, the superhard material100 can be used in or obtained from various other applicationsincluding, but not limited to, machining, woodworking, and quarrying.

Different PCD, PCBN, hard, and superhard material grades are availablefor the cutters 100 to be used in various applications, such as drillingdifferent rock formations using different drill bit designs or machiningdifferent metals or materials. Common problems associated with thesecutters 100 include chipping, spalling, partial fracturing, cracking,and/or flaking of the cutting table 120 during use. These problemsresult in the early failure of the cutting table 120 and/or thesubstrate 110. Typically, high magnitude stresses generated on thecutting table 120 at the region where the cutting table 120 makescontact with earthen formations during drilling can cause theseproblems. These problems increase the cost of drilling due to costsassociated with repair, production downtime, and labor costs. Thus, anend-user, such as a bit designer or a field application engineer,chooses the best performing grade of the cutter 100 for any givendrilling or machining task to reduce these common problems fromoccurring. For example, the end-user selects an appropriate cutter 100by balancing the wear resistance and the impact resistance of the cutter100, as determined using conventional methods. Typically, theinformation available to the end-user for selecting the appropriategrade cutter 100 for a particular application is derived from historicaldata records that show performance of different grades of PCD, PCBN,hard, or superhard material in specific areas and/or from laboratoryfunctional tests which attempt to mimic various drilling or machiningconditions while testing different cutters 100. There are currently twomain categories of laboratory functional testing that are used in thedrilling industry. These tests are the wear abrasion test and the impacttest.

Superhard materials 100, which include polycrystalline diamond compact(“PDC”) cutters 100, have been tested for abrasive wear resistancethrough the use of two conventional testing methods. The PDC cutter 100includes the cutting table 120 fabricated from PCD. FIG. 2 shows a lathe200 for testing abrasive wear resistance using a conventional granitelog test. Although one exemplary apparatus configuration for the lathe200 is provided, other apparatus configurations known to people havingordinary skill in the art can be used without departing from the scopeand spirit of the exemplary embodiment.

Referring to FIG. 2, the lathe 200 includes a chuck 210, a tailstock220, and a tool post 230 positioned between the chuck 210 and thetailstock 220. A target cylinder 250 has a first end 252, a second end254, and a sidewall 258 extending from the first end 252 to the secondend 254. According to the conventional granite log test, sidewall 258 isan exposed surface 259 which makes contact with the superhard component100 during the test. The first end 252 is coupled to the chuck 210,while the second end 254 is coupled to the tailstock 220. The chuck 210is configured to rotate, thereby causing the target cylinder 250 to alsorotate along a central axis 256 of the target cylinder 250. Thetailstock 220 is configured to hold the second end 254 in place whilethe target cylinder 250 rotates. The target cylinder 250 is fabricatedfrom a single uniform material, which is typically granite. However,other rock types have been used for the target cylinder 250, whichincludes, but is not limited to, Jackfork sandstone, Indiana limestone,Berea sandstone, Carthage marble, Champlain black marble, Berkleygranite, Sierra white granite, Texas pink granite, and Georgia graygranite.

The PDC cutter 100 is fitted to the lathe's tool post 230 so that thePDC cutter 100 makes contact with the target cylinder's 250 exposedsurface 259. The lathe's tool post 230 draws the PDC cutter 100 back andforth across the exposed surface 259. The tool post 230 has an inwardfeed rate on the target cylinder 250. The abrasive wear resistance forthe PDC cutter 100 is determined as a wear ratio, which is defined asthe volume of target cylinder 250 that is removed to the volume of thePDC cutter 100 that is removed. Alternatively, instead of measuringvolume, the distance that the PDC cutter 100 travels across the targetcylinder 250 can be measured and used to quantify the abrasive wearresistance for the PDC cutter 100. Alternatively, other methods known topersons having ordinary skill in the art can be used to determine thewear resistance using the granite log test. Operation and constructionof the lathe 200 is known to people having ordinary skill in the art.Descriptions of this type of test is found in the Eaton, B. A., Bower,Jr., A. B., and Martis, J. A. “Manufactured Diamond Cutters Used InDrilling Bits.” Journal of Petroleum Technology, May 1975, 543-551.Society of Petroleum Engineers paper 5074-PA, which was published in theJournal of Petroleum Technology in May 1975, and also found in Maurer,William C., Advanced Drilling Techniques, Chapter 22, The PetroleumPublishing Company, 1980, pp. 541-591, which is incorporated byreference herein.

FIG. 3 shows a vertical boring mill 300 for testing abrasive wearresistance using a vertical boring mill (“VBM”) test or vertical turretlathe (“VTL”) test. Although one exemplary apparatus configuration forthe VBM 300 is provided, other apparatus configurations can be usedwithout departing from the scope and spirit of the exemplary embodiment.The vertical boring mill 300 includes a rotating table 310 and a toolholder 320 positioned above the rotating table 310. A target cylinder350 has a first end 352, a second end 354, and a sidewall 358 extendingfrom the first end 352 to the second end 354. According to theconventional VBM test, second end 354 is an exposed surface 359 whichmakes contact with a superhard material 100 during the test. The targetcylinder 350 is typically about thirty inches to about sixty inches indiameter; however, this diameter can be greater or smaller.

The first end 352 is mounted on the lower rotating table 310 of the VBM300, thereby having the exposed surface 359 face the tool holder 320.The PDC cutter 100 is mounted in the tool holder 320 above the targetcylinder's exposed surface 359 and makes contact with the exposedsurface 359. The target cylinder 350 is rotated as the tool holder 320cycles the PDC cutter 100 from about the center of the target cylinder'sexposed surface 359 out to about its edge and back again to about thecenter of the target cylinder's exposed surface 359. The tool holder 320has a predetermined downward feed rate. The VBM method allows for higherloads to be placed on the PDC cutter 100 and the larger target cylinder350 provides for a greater rock volume for the PDC cutter 100 to act on.The target cylinder 350 is typically fabricated from granite; however,the target cylinder can be fabricated from other materials that include,but is not limited to, Jackfork sandstone, Indiana limestone, Bereasandstone, Carthage marble, Champlain black marble, Berkley granite,Sierra white granite, Texas pink granite, and Georgia gray granite.

The abrasive wear resistance for the PDC cutter 100 is determined as awear ratio, which is defined as the volume of target cylinder 350 thatis removed to the volume of the PDC cutter 100 that is removed.Alternatively, instead of measuring volume, the distance that the PDCcutter 100 travels across the target cylinder 350 can be measured andused to quantify the abrasive wear resistance for the PDC cutter 100.Alternatively, other methods known to persons having ordinary skill inthe art can be used to determine the wear resistance using the VBM test.Operation and construction of the VBM 300 is known to people havingordinary skill in the art. A description for this type of testing can befound in Bertagnolli, Ken and Vale, Roger, “Understanding andControlling Residual Stresses in Thick Polycrystalline Diamond Cuttersfor Enhanced Durability,” US Synthetic Corporation, 2000, which isincorporated by reference in its entirety herein.

In addition to testing for abrasive wear resistance, PDC cutters 100also can be tested for resistance to impact loading. FIG. 4 shows a droptower apparatus 400 for testing impact resistance of superhardcomponents using a “drop hammer” test where a metal weight 450 issuspended above and dropped onto the cutter 100. The “drop hammer” testattempts to emulate the type of loading that can be encountered when thePDC cutter 100 transitions from one formation to another or experienceslateral and axial vibrations. Results from the impact testing allows forranking different cutters based upon their impact strength; however,these ranking do not allow for predictions to be made according to howthe cutters 100 will perform in the actual field.

Referring to FIG. 4, the drop tower apparatus 400 includes a superhardmaterial 100, such as a PDC cutter, a target fixture 420, and a strikeplate 450 positioned above the superhard material 100. The PDC cutter100 is locked into the target fixture 420. The strike plate 450, orweight, is typically fabricated from steel and is positioned above thePDC cutter 100. However, the strike plate 450 can be fabricated fromalternative materials known to persons having ordinary skill in the art.The PDC cutter 100 is typically held at a backrake angle 415 with thediamond table 120 of the PDC cutter 100 angled upward towards the strikeplate 450. The range for the backrake angle 415 is known to peoplehaving ordinary skill in the art.

The strike plate 450 is repeatedly dropped down on the edge of the PDCcutter 100 until the edge of the PDC cutter 100 breaks away or spallsoff. These tests are also referred to as “side impact” tests because thestrike plate 450 impacts an exposed edge of the diamond table 120.Failures typically appear in either the diamond table 120 or at thecontact face 115 between the diamond table 120 and the carbide substrate110. The “drop hammer” test is very sensitive to the edge geometry ofthe diamond table 120. If the table 120 is slightly chamfered, the testresults can be altered considerably. The total energy, expressed inJoules, expended to make the initial fracture in the diamond table 120is recorded. For more highly impact resistant cutters 100, the strikeplate 450 can be dropped according to a preset plan from increasingheights to impart greater impact energy on the cutter 100 to achievefailure. However, this “drop hammer” test embodies drawbacks in thatthis method requires that many cutters 100 be tested to achieve a validstatistical sampling that can compare the relative impact resistance ofone cutter type to another cutter type. The test is inadequate inproviding results that reflect the true impact resistance of the entirecutter 100 as it would see impact loads in a downhole environment. Thetest exhibits a static impact effect whereas the true impact is dynamic.The number of impacts per second can be as high as 100 hertz (“Hz”).Also, the amount of damage to the cutter 100 is subjectively evaluatedby someone with a trained eye and is compared to damages incurred byother cutters.

While the results for different wear tests available in the market havegenerally a reasonable degree of agreement with the actual fieldperformance, the same is not the case for the results of conventionalimpact tests. Although there is some degree of correlation between theresults of conventional impact tests and actual field performance, thescattering of the data is usually very large, thereby causingpredictions on how cutters will behave in actual field performance to bedifficult and/or inaccurate. Also, many fractures occurring within thecutter are not detected using these conventional tests and therefore goundetected when evaluating the toughness of the cutter.

Additionally, since the bit selection is a critical process, it isimportant to know the mechanical properties of the different rocks, orrock formations, the bit is to drill through. One of the most importantparameters currently used for the bit selection is the unconfinedcompressive strength (“UCS”) of the rock, which can be measured directlyon core samples obtained from the rock formations within the wellbore orevaluated indirectly from log data. However, the UCS of the rock shouldnot be solely relied on when selecting the bit because the UCS can bemisleading, especially when the rock UCS is greater than 15000 psi andis brittle, thereby having a low fracture toughness K_(1C). Thus,fracture toughness of the rock should also be considered when selectingthe proper drill bit.

In oil well drilling and completion operations, it is beneficial to knowthe compressive strength of various rock formations within the wellplan. These compressive strengths can be used to plan drillingoperations since, as previously mentioned, the compressive strengthaffects the drill bit selection and casing plan among other drillingoperations. For completions operations, it is beneficial to know thecompressive strength to plan fracturing operations. One method used fordetermining the compressive strength of a rock formation within thewellbore is to calculate the compressive strength from electric logdata, such as sonic logs, electric resistivity, and gamma logs. However,inaccuracies occur when calculating compressive strength from electriclog data. Inaccuracies develop because log interpretation requires somecalibration with core data. Another method used for determining thecompressive strength of a rock formation within the wellbore is toretrieve a core sample, or rock sample, from the rock formation withinthe wellbore and directly measure the compressive strength. However,inaccuracies also occur when directly measuring the compressive strengthfrom a retrieved core sample. Inaccuracies develop because thecalculated compressive strength is performed at the surface and not inthe wellbore; and therefore, it is the unconfined compressive strength(“UCS”) that is determined rather than the confined compressive strength(“CCS”).

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the invention are bestunderstood with reference to the following description of certainexemplary embodiments, when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 shows a superhard material that is insertable within a downholetool in accordance with an exemplary embodiment of the invention;

FIG. 2 shows a lathe for testing abrasive wear resistance using aconventional granite log test;

FIG. 3 shows a vertical boring mill for testing abrasive wear resistanceusing a vertical boring mill test or vertical turret lathe test;

FIG. 4 shows a drop tower apparatus for testing impact resistance ofsuperhard components using a “drop hammer” test;

FIG. 5 shows a perspective view of an acoustic emission testing systemin accordance with an exemplary embodiment of the present invention;

FIG. 6 shows a cross-sectional view of the acoustic emission testingdevice of FIG. 5 in accordance with an exemplary embodiment of thepresent invention;

FIG. 7 shows a perspective view of a cutter holder, as shown in FIG. 5,in accordance with an exemplary embodiment of the present invention;

FIG. 8 shows a perspective view of the acoustic emission testing deviceof FIG. 5 with the indenter being removed from the cutter holder inaccordance with an exemplary embodiment of the present invention;

FIG. 9 shows a perspective view of an acoustic emission testing systemin accordance with an alternative exemplary embodiment of the presentinvention;

FIG. 10 shows a schematic block diagram of a data recorder of FIG. 5 inaccordance with an exemplary embodiment;

FIG. 11 shows a graphical cutter acoustic emission and loadingrepresentation for a cutter experiencing a load of up to about twokilonewtons in accordance with an exemplary embodiment of the presentinvention;

FIG. 12 shows a graphical cutter acoustic emission and loadingrepresentation for a cutter experiencing a load of up to about fivekilonewtons in accordance with an exemplary embodiment of the presentinvention;

FIG. 13 shows a graphical cutter acoustic emission and loadingrepresentation for a cutter experiencing a load of up to about thirtykilonewtons in accordance with an exemplary embodiment of the presentinvention;

FIG. 14 shows a graphical cutter acoustic emission and loadingrepresentation for a cutter experiencing a load of up to about fortykilonewtons in accordance with an exemplary embodiment of the presentinvention;

FIG. 15A shows a graphical cutter acoustic emission and loadingrepresentation for a cutter manufacturer #1 cutter sample #1 cutter typeexperiencing a load of up to about forty-five kilonewtons in accordancewith an exemplary embodiment of the present invention;

FIG. 15B shows a graphical cutter acoustic emission and loadingrepresentation for a cutter manufacturer #2 cutter sample #2 cutter typeexperiencing a load of up to about thirty kilonewtons in accordance withan exemplary embodiment of the present invention;

FIG. 16 illustrates a flowchart of a method for analyzing data pointsreceived from the acoustic sensor, wherein the method includes a loopone method and a loop two method in accordance with an exemplaryembodiment of the present invention;

FIG. 17 illustrates a detailed flowchart of the loop one method of FIG.16 in accordance with an exemplary embodiment of the present invention;

FIG. 18 illustrates a detailed flowchart of the loop two method of FIG.16 in accordance with an exemplary embodiment of the present invention;

FIG. 19 shows a graphical cutter acoustic emission representation for acutter experiencing a load in accordance with an exemplary embodiment ofthe present invention;

FIG. 20 shows a magnified view of a portion of a graphical cutteracoustic emission representation for a cutter experiencing a load inaccordance with an exemplary embodiment of the present invention;

FIG. 21 shows a cumulative distribution representation for each actualacoustic event in accordance with an exemplary embodiment of the presentinvention;

FIG. 22 shows a block diagram of the processor of FIG. 10 in accordancewith an exemplary embodiment;

FIG. 23 shows a rock sample that is testable within the acousticemission testing systems of FIGS. 5 and 9, respectively, in lieu of thecutter of FIG. 1 in accordance with an exemplary embodiment;

FIG. 24 shows the acoustic emission testing device of FIG. 5 insertedwithin a pressurizable chamber in accordance with an exemplaryembodiment;

FIG. 25 shows a cross-sectional view of an acoustic emission testingsystem in accordance with an exemplary embodiment of the presentinvention;

FIG. 26 shows a cross-sectional view of an acoustic emission testingsystem in accordance with another exemplary embodiment of the presentinvention;

FIG. 27 shows an acoustic testing method in accordance with an exemplaryembodiment of the present invention;

FIG. 28 shows a cross-sectional view of an acoustic emission testingsystem in accordance with yet another exemplary embodiment of thepresent invention;

FIG. 29 shows a side schematic view of an acoustic emission formationsampling tool in an operating position within a wellbore in accordancewith another exemplary embodiment of the present invention;

FIG. 30 shows a top schematic view of an acoustic emission formationsampling tool in an operating position within a wellbore in accordancewith another exemplary embodiment of the present invention;

FIG. 31 shows a side schematic view of an acoustic emission formationsampling tool in an operating position within a wellbore in accordancewith another exemplary embodiment of the present invention; and

FIG. 32 illustrates a flowchart of a method for determining one or moreproperties of a rock formation located within a wellbore using theacoustic emission formation sampling tool in accordance with anexemplary embodiment of the present invention.

The drawings illustrate only exemplary embodiments of the invention andare therefore not to be considered limiting of its scope, as theinvention may admit to other equally effective embodiments.

BRIEF DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention is directed to a method, apparatus, and softwarefor testing the intrinsic strength, or toughness, of hard or superhardmaterials, such as inserts and rock samples obtained from a down holeformation, using acoustic emissions. Although the description ofexemplary embodiments is provided below in conjunction with a PDCcutter, alternate embodiments of the invention may be applicable toother types of hard or superhard materials including, but not limitedto, PCBN cutters, rock samples, or other hard or superhard materialsknown or not yet known to persons having ordinary skill in the art. Forexample, the hard or superhard materials include cemented tungstencarbide, silicon carbide, tungsten carbide matrix coupons, ceramics, orchemical vapor deposition (“CVD”) coated inserts. The hard or superhardmaterials also include rock samples that include, but are not limitedto, hard rock samples and/or cemented rock samples obtained from a downhole formation or drill hole. According to some exemplary embodiments ofthe present invention, one or more properties of a rock sample isdetermined by measuring the fracture events occurring within the rocksample when subjected to fracture-causing pressures. In certainexemplary embodiments, the fracture events are measured over time andspace. Measuring at least the intensity and/or the locations of thefractures within the rock sample facilitate in selecting the appropriatecutter types to be used for the drilling application according to someexemplary embodiments. In some exemplary embodiments, measuring at leastthe intensity and/or the locations of the fractures within the rocksample facilitate in selecting at least one parameter of a high pressuredown hole fracturing program or at least one parameter of a down holedrilling program targeted to the down hole formation or similar downhole formations from which the rock sample was obtained. In someexemplary embodiments, measuring at least the intensity and/or thelocations of fractures within the rock sample facilitate in selecting atleast one parameter of a perforating program for explosive, bullet,abrasive, or hydraulic jet perforating through a liner and into theformation to be produced. In some exemplary embodiments, measuring atleast the intensity and/or the locations of fractures within the rocksample facilitate a correlation to rock porosity. In some exemplaryembodiments, measuring at least the intensity and/or the locations offractures within the rock sample facilitate a direct measurement of rockdensity. In some exemplary embodiments, measuring at least the intensityand/or the locations of fractures within the rock sample facilitate thedesign of a well completion program.

The invention is better understood by reading the following descriptionof non-limiting, exemplary embodiments with reference to the attacheddrawings, wherein like parts of each of the figures are identified bylike reference characters, and which are briefly described as follows.FIG. 5 shows a perspective view of an acoustic emission testing system500 in accordance with an exemplary embodiment of the present invention.FIG. 6 shows a cross-sectional view of the acoustic emission testingdevice 505 of FIG. 5 in accordance with an exemplary embodiment of thepresent invention. Referring to FIGS. 5 and 6, the acoustic emissiontesting system 500 includes an acoustic emission testing device 505communicably coupled to a data recorder 590. The acoustic emissiontesting device 505 includes a cutter holder 510, the cutter 100, anindenter 550, and an acoustic sensor 570. In certain embodiments,however, the cutter holder 510 is optional. Although the cutter 100 isdepicted in the exemplary embodiment, a rock sample 2300 (FIG. 23)replaces the cutter 100 in alternative exemplary embodiments.

FIG. 7 shows a perspective view of the cutter holder 510 in accordancewith an exemplary embodiment of the present invention. Referring toFIGS. 5, 6, and 7, the cutter holder 510 includes first surface 712, asecond surface 714, and a side surface 716. The first surface 712 isdisposed in a plane that is substantially parallel to the plane that thesecond surface 714 is disposed. The side surface 716 extends from thefirst surface 712 to the second surface 714. According to some exemplaryembodiments, the side surface 716 is substantially perpendicular to atleast one of the first surface 712 and the second surface 714. Accordingto alternative exemplary embodiments, the side surface 716 is notsubstantially perpendicular to either the first surface 712 or thesecond surface 714. The cutter holder 510 is fabricated from steel;however, according to other exemplary embodiments, the cutter holder 510is fabricated from any metal, wood, or other suitable material known topeople having ordinary skill in the art that is capable of withstandinga load 580, which is described in further detail below, that is to beapplied. The load 580 can range from about zero kilonewtons to aboutseventy kilonewtons. In certain exemplary embodiments, the suitablematerial is capable of being machined or molded and is capable ofpropagating sound. In certain exemplary embodiments, the suitablematerial is capable of propagating sound at a speed of about 1kilometers per second or higher.

The cutter holder 510 is shaped in a substantially cylindrical shape,wherein the first surface 712 is substantially circular shaped, thesecond surface is substantially circular shaped, and the side surface716 is substantially arcuate shaped. However, the side surface 716includes a coupling portion 730, which is substantially planar, orflat-surfaced, and extends from the first surface 712 to the secondsurface 714. The coupling portion 730 provides a surface for couplingthe acoustic sensor 570 to the cutter holder 510. In certain exemplaryembodiments, the coupling portion 730 does not extend the entire lengthfrom the first surface 712 to the second surface 714. In some exemplaryembodiments, the acoustic sensor 570 is sized such that the acousticsensor 570 is able to be coupled to the side surface 716 that is arcuateshaped. Thus, the coupling portion 730 is optional in those exemplaryembodiments. Although one exemplary shape is provided for the cutterholder 510, the cutter holder 510 can be shaped into any other geometricor non-geometric shape, such as square shaped cylinder or triangularshaped cylinder, without departing from the scope and spirit of theexemplary embodiment.

A cavity 720 is formed within the cutter holder 510 and is sized toreceive the cutter 100, or some other hard or superhard material such asa rock sample 2300 (FIG. 23), which is further described below. Thecavity 720 is sized slightly larger in diameter than the diameter of thecutter 100, thereby allowing the cutter 100 to easily and freely fitwithin the cavity 720. The cavity 720 extends from the first surface 712towards the second surface 714, but does not reach the second surface714. In other exemplary embodiments, the cavity 720 extends from thefirst surface 712 to the second surface 714 and proceeds through thecutter holder 510, thereby forming a hole within the cutter holder 510.The cavity 720 is circular in shape, but is any other geometric ornon-geometric shape in other exemplary embodiments. The cavity 720 isformed by machining the cutter holder 510 or molding the cutter holder510 to have the cavity 720 formed therein. Alternatively, the cavity 720is formed using other methods known to people having ordinary skill inthe art. In certain exemplary embodiments, the cavity 720 is formed in amanner to ensure that the cutter 100 is properly aligned in the samemanner each time the cutter 100 is inserted within the cavity 720.

The cutter 100 has been previously described with respect to FIG. 1 andis applicable to the exemplary embodiments. Briefly, the cutter 100includes the substrate 110 and the cutter table 120, which is formed orcoupled to the top of the substrate 110. In the exemplary embodiment,the cutter table 120 is formed from PCD, but alternative exemplaryembodiments have the cutter table 120 fabricated from other materials,such as PCBN, without departing from the scope and spirit of theexemplary embodiment. Although cutter 100 has a planar cutter table 120,or is flat-faced, the cutter table 120 can be dome shaped, concaveshaped, or any other shape known to people having ordinary skill in theart.

The cutter 100 includes finished and/or grounded cutters as well as“raw” cutters. “Raw” cutters are unfinished and are cutters that aretypically available right out of a pressing cell. Embodiments of thepresent invention allow testing of both these cutter types. Since cuttermanufacturers are able to test “raw” cutters in accordance withembodiments of the present invention, cutter manufacturers are able toinsure that they are meeting specification early in a cutter productionrun. If cutter manufacturers determine that the “raw” cutters 100 arenot meeting appropriate specifications, they are able to make thenecessary changes in their operating parameters to get “good” cuttersbefore continuing on with the cutter production run. Additionally, “raw”cutters are capable of being tested at a lower kilonewton level, orload, to insure that the “raw” cutters are not cracking under the givenload. If cracks are occurring during the testing of the “raw” cutters,cutter manufacturers can forgo the additional expenses associated withfinishing and grinding these “raw” cutters; thereby saving unnecessarycost expenditures. Hence, each “raw” cutter is capable of being testedthrough the acoustic emission testing system 500 using lower load levelsto insure that the cutters 100 are “good” cutters.

Referring to FIG. 6, the cutter 100 is inserted within the cavity 720 ofthe cutter holder 510. The cutter 100 is oriented within the cavity 720so that the cutter table 120 is facing towards the first surface 712, oraway from the second surface 714. According to this exemplaryembodiment, the entire cutter 100 is inserted within the cavity 720.However, in alternative exemplary embodiments, a portion of the cutter100, which includes the entire substrate 110, is completely insertedwithin the cavity 720. Thus, in these alternative exemplary embodiments,at least a portion of the cutter table 120 is not inserted within thecavity 720. Once the cutter 100 has been inserted within the cavity 720,an air gap 610 is formed between the outer perimeter of the cutter 100and the outer surface of the cavity 720. According to certain exemplaryembodiments, a lubricant 620 is applied to the outer perimeter of thecutter 100 or placed within the cavity 720. In these exemplaryembodiments, once the cutter 100 is placed within the cavity 720, thelubricant 620 fills at least a portion of the air gap 610 such that thelubricant 620 adheres to both the outer surface of the cavity 720 andthe outer perimeter of the cutter 100 and occupies the portion of theair gap 610 therebetween. In other exemplary embodiments, the lubricant620 is placed at least between the bottom surface of the cavity 720 andthe base of the cutter 100. The lubricant 620 improves acoustictransmission between the cutter 100 and the acoustic sensor 570. Thelubricant 620 is a gel, such as an ultrasound gel, according to someexemplary embodiments. However, in alternative exemplary embodiments,other materials can be used as the lubricant 620, which includes, but isnot limited to, oils, greases, and lotions. These materials are capableof being spread, adhering to surfaces, and not rapidly drying out.Although the cutter 100 is described as being used in this exemplaryembodiment, other hard or superhard materials that desire a toughnesstesting can be used in lieu of the cutter 100.

Referring back to FIGS. 5 and 6, the indenter 550 is dome shaped at afirst end 650 and has a planar surface at a second end 652. The indenter550 is fabricated to be tougher than the cutter 100 so that once load580 is applied to the indenter 550, it is the cutter 100 that is damagedand not the indenter 550. For example, the indenter 550 is fabricatedfrom tungsten carbide-cobalt; however, other materials known to thosehaving ordinary skill in the art can be used to fabricate the indenter550. In certain exemplary embodiments, the cobalt content of theindenter 550 ranges from about six percent to about twenty percent. Incertain exemplary embodiments, the cobalt content of the indenter 550 isgreater than the cobalt content of the cutter table 120 of the cutter100. Additionally, in certain exemplary embodiments, a PCD layer isformed or mounted onto the first end 650 of the indenter 550. In theseembodiments, the cobalt content of the PCD layer of the indenter 550 isgreater than the cobalt content of the cutter table 120 of the cutter100. Also, in these exemplary embodiments, the cobalt content of the PCDlayer of the indenter 550 ranges from about six percent to about twentypercent. Although cobalt is used in these exemplary embodiments to makethe indenter tougher than the cutter 100, other components known topeople having ordinary skill in the art can be used in alternativeexemplary embodiments.

The indenter 550 is sized to fit within the cavity 720 so that it makescontact with the cutter 100. In certain exemplary embodiments, theperimeter of the indenter 550 is sized substantially similar to theperimeter of the cavity 720. However, in the exemplary embodiments whereat least a portion of the cutter table 120 is not within the cavity 720,the indenter 550 can be dimensioned such that the perimeter of theindenter 550 is greater than the perimeter of the cavity 720. Theindenter 550 is oriented so that the first end 650 makes contact withthe cutter 100. Thus, in this embodiment, the PDC layer of the indenter550 makes contact with the PDC layer, or cutter table 120, of the cutter100. The load 580 is applied to the second end 652, which transmits theload 580 onto the cutter 100. Although a dome shaped indenter 550 isused in these exemplary embodiments, other exemplary embodiments can useindenters having other shapes, such as a cylindrical shape having asubstantially planar surface at both the first end 650 and the secondend 652. Also, the second end 652 can be formed into other non-planarshapes without departing from the scope and spirit of the exemplaryembodiments.

The acoustic sensor 570 is a piezoelectric sensor that is positionedalong the coupling portion 730 of the cutter holder 510. However, theacoustic sensor 570 can be any other device type known to people havingordinary skill in the art, wherein the device is capable of detectingacoustic transmissions. The acoustic sensor 570 detects elastic wavesignals formed in the cutter 100, which then converts the elastic wavessignal to a voltage signal so that the data can be recorded andsubsequently analyzed. In certain exemplary embodiments, the lubricant620 is placed at the contact area between the coupling portion 730 andthe acoustic sensor 570. As previously mentioned, the lubricant 620improves detection of elastic wave transmission from the cutter 100 tothe acoustic sensor 570. According to some alternative exemplaryembodiments, the acoustic sensor 570 is sized so that it is capable ofbeing placed on the arcuate portion of the side surface 716. Theacoustic sensor 570 is communicably coupled to the data recorder 590 sothat the voltage signal derived from the elastic waves occurring withinthe cutter 100 can be stored and subsequently analyzed. The acousticsensor 570 is coupled to the data recorder 590 using a cable 592;however, according to other exemplary embodiments, the acoustic sensor570 can be communicably coupled to the data recorder 590 wirelesslyusing wireless technology including, but not limited to, infrared andradio frequency.

The data recorder 590 records the data sent from the acoustic sensor 570and stores the data therein. In certain exemplary embodiments, theapparatus (not shown), or machine, delivering the load 580 also iscoupled to the data recorder 590 using a cable 582; however, accordingto other exemplary embodiments, the apparatus delivering the load 580can be communicably coupled to the data recorder 590 wirelessly usingwireless technology including, but not limited to, infrared and radiofrequency. The data recorder 590 also processes and analyzes the datathat it receives. Although the

FIG. 10 shows a schematic block diagram of a data recorder 590 of FIG. 5in accordance with an exemplary embodiment. Referring to FIGS. 5 and 10,the data recorder 590 is a computer system. The data recorder 590includes a storage medium 1040, a user interface 1030, a processor 1020,and a display 1010.

The storage medium 1040 receives information from the acoustic sensor570 (FIG. 5) and records the information therein. The storage medium1040 is a hard drive according to one exemplary embodiment. However,according to other exemplary embodiments, the storage medium 1040includes at least one of a hard drive, a portable hard drive, a USBdrive, a DVD, a CD, or any other device capable of storing data and/orsoftware. In some exemplary embodiments, the storage medium 1040 alsoincludes a software for providing instructions on how to process theinformation, or data, received from the acoustic sensor 570 (FIG. 5).

The user interface 1030 allows a user to interface with the datarecorder 590 and provide instructions for operating the data recorder590. According to some exemplary embodiments, the user interfaceincludes a keyboard. However, according to other exemplary embodiments,the user interface includes at least one of a keyboard, a mouse, a touchscreen which can be part of the display 1010, or any other userinterface known to people having ordinary skill in the art.

The processor 1020 is capable of receiving instructions from the userinterface 1030, accessing information stored within the storage medium1040, sending information to the storage medium 1040, and sendinginformation to the display 1010. In some exemplary embodiments, theprocessor 1020 accesses the software that resides within the storagemedium 1040 and executes the set of instructions provided by thesoftware. A more detailed description of these instructions are providedfurther below. In some exemplary embodiments, the processor 1020includes processor engines 2200, which are described in further detailbelow in conjunction with FIGS. 16, 17, 18, and 22.

The display 1010 receives information from the processor andcommunicates this information to the user. According to one exemplaryembodiment, the display 1010 includes a monitor, or screen. However,according to other exemplary embodiments, the display 1010 includes atleast one of a screen, a touch screen, a printer, or any other devicecapable of communicating information to the user.

Although not illustrated in FIG. 10, the data recorder 590 can becommunicably coupled, either wired or wirelessly, to an internalnetwork, wherein the software and/or data from the acoustic sensor 570(FIG. 5) is stored in a central server (not shown). Additionally,according to some alternative exemplary embodiments, the data recorder590 can be communicably coupled, either wired or wirelessly, to a modem(not shown), wherein the modem is communicably coupled to the world wideweb. In certain alternative exemplary embodiments, the software and/ordata from the acoustic sensor 570 (FIG. 5) is stored in a remotelocation that is accessible via the world wide web.

FIG. 8 shows a perspective view of the acoustic emission testing device505 of FIG. 5 with the indenter 550 being removed from the cutter holder510 in accordance with an exemplary embodiment of the present invention.Referring to FIG. 8, the cutter 100 is fully inserted within the cavity720 of the cutter holder 510. As shown, the diameter of the cutter 100is less than the diameter of the cavity 720, thereby forming the airgaps 610. Also, the PDC layer, or the cutter table 120, is orientedwithin the cavity 720 so that the PCD layer faces towards the firstsurface 712. The indenter 550 is removed from the cavity 720 to furtherillustrate some features of the indenter 550. According to thisexemplary embodiment, the indenter 550 includes a substrate 808 and ahard surface 810, which is formed or coupled to the top of the substrate808. In the exemplary embodiment, the hard surface 810 is formed fromPCD, but alternative exemplary embodiments can have the hard surface 810fabricated from other hard or superhard materials, such as PCBN, withoutdeparting from the scope and spirit of the exemplary embodiment.Although indenter 550 has a dome shaped hard surface 810, the hardsurface 810 can be planar or any other shape known to people havingordinary skill in the art. As seen, the indenter 550 has a diametersubstantially similar to the diameter of the cavity 720, according tothis exemplary embodiment.

In an alternative embodiment, the indenter 550 is positioned within thecavity 720 having the hard surface 810 facing towards the first surface712. The cutter 100 to be tested is positioned on top of the indenter550 with the cutter table 120 contacting the hard surface 810. The load580 is applied downward on the back face of the substrate 110 of thetest cutter 100. Acoustic emissions of cracks initiated and/orpropagated in the test cutter 100 is transmitted through the indenter550 and to the acoustic sensor 570. In this alternative exemplaryembodiment, the cutter holder 510 is optional.

FIG. 9 shows a perspective view of an acoustic emission testing system900 in accordance with an alternative exemplary embodiment of thepresent invention. Referring to FIG. 9, the acoustic emission testingsystem 900 includes an acoustic emission testing device 905 communicablycoupled to the data recorder 507. The acoustic emission testing device905 is similar to the acoustic emission testing device 505 of FIG. 5,except that the acoustic sensor 570 is directly coupled to the cutter100 and the cutter holder 510 of FIG. 5 is removed. The cutter 100, theindenter 550, the load 580, the acoustic sensor 570, and the datarecorder 590 have been previously described with respect to FIGS. 5, 6,7, 8, and 10. Also, the lubricant 620 (FIG. 6) is placed between theacoustic sensor 570 and the cutter 100 according to some exemplaryembodiments.

The operation of the acoustic emission testing system 500 is describedwhile referring to FIGS. 5-8. The cutter 100, or hard or superhardmaterial, to be tested is placed within the cavity 720 of the cutterholder 510. To improve the elastic wave transmission across thecontacting surfaces between the base, or bottom surface, of the cutter100 and the base of the cavity 720, a mineral oil based gel 620 is usedbetween the bottom surface of the cutter 100 and the base of the cavity720. The acoustic sensor 570 is positioned against the coupling portion730 of the cutter holder 510 to detect the elastic waves generatedwithin the cutter 100. To improve the elastic wave transmission acrossthe contacting surfaces between the acoustic sensor 570 and the couplingportion 730, the mineral oil based gel 620 also is used between theacoustic sensor 570 and the coupling portion 730. The indenter 550 isplaced on top of the PCD layer 120 of the cutter 100 and is pushedagainst this PCD layer 120 using the load 580. The load 580 is providedon the indenter 550 using a 100 kilonewton 8500 series Instron machine.This machine (not shown) is capable of controlling the amount of loadthat is exerted on the indenter 550. The machine is hooked up to thedata recorder 590 so that load versus time is measured. Although oneexample of a machine capable of providing the load 580 is disclosed, anysystem capable of providing a measurable load to the indenter 550 is inthe scope of exemplary embodiments for this invention. For example, themachine or apparatus for delivering the measurable load 580 can rangefrom a handheld hammer to a fully instrumented impact machine or to aload controlled hydraulic machine for steady ramp or cyclic loadinghistories.

The load 580 is applied onto the indenter 550 and increased at aconstant rate to a desired load level. Once reaching the desired loadlevel, the load level is maintained for a desired period of time, whichcan range from a few seconds to several minutes, and then ramped down ata faster rate than the ramp up rate. Each time a new crack forms or anexisting crack grows within the top diamond layer 130, a certain amountof elastic energy is released almost instantaneously in the form of atrain of elastic waves travelling through the PCD layer 120, thesubstrate 110, and the cutter holder 510. The acoustic sensor 570detects these elastic waves and converts the received signals into avoltage signal. The acoustic sensor 570 is communicably coupled to thedata recorder 590 so that acoustic emissions, or data, are recordedagainst time. These acoustic emissions include background noise andacoustic events. Hence, since the acoustic emissions history and theloading history is recorded onto the data recorder 590, one candetermine at what load 580 certain acoustic events occurred. An acousticevent is an event where a new crack forms or when an existing crackgrows in the PDC layer 120. According to one exemplary embodiment, theacoustic sensor 570 provides data to the data recorder 590 at about5,000 data points per second; however, the data points per second can beincreased or decreased without departing from the scope and spirit ofthe exemplary embodiment.

FIG. 11 shows a graphical cutter acoustic emission and loadingrepresentation 1100 for a cutter experiencing a load of up to about twokilonewtons in accordance with an exemplary embodiment of the presentinvention. Referring to FIG. 11, the cutter acoustic emission andloading representation 1100 includes a time axis 1110, a load axis 1120,and an acoustic emissions axis 1130. The time axis 1110 is representedby an x-axis and is provided with units in the seconds times 5,000.Thus, to obtain the time period in seconds, the numerical value in thetime axis 1110 is to be divided by 5,000. The time axis 1110 can also beread as energy being delivered to the sample. In other words, as moretime passes, more total energy is exerted on the cutter or test sample.The load axis 1120 is represented by a y-axis and is provided with unitsin the kilonewtons. The acoustic emissions axis 1130 also is representedby the y-axis and is provided with units in the millivolts times ten.Thus, to obtain the voltage in millivolts, the numerical value in theacoustic emissions axis 1130 is to be divided by ten. A load curve 1140and an acoustic emissions curve 1160 are both illustrated on the cutteracoustic emission and loading representation 1100. According to the loadcurve 1140, the load was increased from zero kilonewtons to twokilonewtons at a constant rate 1142, or ramp up rate. The load was heldat a peak load level 1143, or two kilonewtons in this example, for aperiod of time and then ramped down at a ramp down rate 1144, which isfaster than the ramp up rate 1142. The acoustic emissions curve 1160represents the recorded signal from the acoustic sensor. According tothe acoustic emissions curve 1160, the only acoustic emissions recordedis a background noise 1162. There were no acoustic events that weredetected. Also, as the load increases, the background noise 1162 alsoincreases.

FIG. 12 shows a graphical cutter acoustic emission and loadingrepresentation 1200 for a cutter experiencing a load of up to about fivekilonewtons in accordance with an exemplary embodiment of the presentinvention. Referring to FIG. 12, the cutter acoustic emission andloading representation 1200 includes a time axis 1210, a load axis 1220,and an acoustic emissions axis 1230. The time axis 1210 is representedby an x-axis and is provided with units in the seconds times 5,000.Thus, to obtain the time period in seconds, the numerical value in thetime axis 1210 is to be divided by 5,000. The time axis 1210 can also beread as energy being delivered to the sample. In other words, as moretime passes, more total energy is exerted on the cutter or test sample.The load axis 1220 is represented by a y-axis and is provided with unitsin the kilonewtons. The acoustic emissions axis 1230 also is representedby the y-axis and is provided with units in the millivolts times ten.Thus, to obtain the voltage in millivolts, the numerical value in theacoustic emissions axis 1230 is to be divided by ten. A load curve 1240and an acoustic emissions curve 1260 are both illustrated on the cutteracoustic emission and loading representation 1200. According to the loadcurve 1240, the load was increased from zero kilonewtons to fivekilonewtons at a constant rate 1242, or ramp up rate. The load was heldat a peak load level 1243, or five kilonewtons in this example, for aperiod of time and then ramped down at a ramp down rate 1244, which isfaster than the ramp up rate 1242. The acoustic emissions curve 1260represents the recorded signal from the acoustic sensor. According tothe acoustic emissions curve 1260, the only acoustic emissions recordedis a background noise 1262. There were no acoustic events that weredetected. Also, as the load increases, the background noise 1262 alsoincreases.

FIG. 13 shows a graphical cutter acoustic emission and loadingrepresentation 1300 for a cutter experiencing a load of up to aboutthirty kilonewtons in accordance with an exemplary embodiment of thepresent invention. Referring to FIG. 13, the cutter acoustic emissionand loading representation 1300 includes a time axis 1310, a load axis1320, and an acoustic emissions axis 1330. The time axis 1310 isrepresented by an x-axis and is provided with units in the seconds times5,000. Thus, to obtain the time period in seconds, the numerical valuein the time axis 1310 is to be divided by 5,000. The time axis 1310 canalso be read as energy being delivered to the sample. In other words, asmore time passes, more total energy is exerted on the sample. The loadaxis 1320 is represented by a y-axis and is provided with units in thekilonewtons. The acoustic emissions axis 1330 also is represented by they-axis and is provided with units in the millivolts times ten. Thus, toobtain the voltage in millivolts, the numerical value in the acousticemissions axis 1330 is to be divided by ten. A load curve 1340 and anacoustic emissions curve 1360 are both illustrated on the cutteracoustic emission and loading representation 1300. According to the loadcurve 1340, the load was increased from zero kilonewtons to thirtykilonewtons at a constant rate 1342, or ramp up rate. The load was heldat a peak load level 1343, or thirty kilonewtons in this example, for aperiod of time and then ramped down at a ramp down rate 1344, which isfaster than the ramp up rate 1342. The acoustic emissions curve 1360represents the recorded signal from the acoustic sensor. According tothe acoustic emissions curve 1360, the acoustic emissions recordedincludes a background noise 1362 and one or more acoustic events 1364.The background noise 1362 makes up the bulk of the data recorded duringthe test. The acoustic events 1364 are shown as thin vertical lines thatsignificantly extend upwards from the background noise 1362. The heightof each acoustic event 1364 above the background noise 1362 isproportional to the amount of elastic energy released by each crackingformation and/or propagation event by means of a calibration constant.Every single acoustic event 1364 lasts on average about fiftymilliseconds. According to this exemplary embodiment, the acousticsensor samples about 5,000 data points per second, which allowsdetection of these acoustic events 1364. Also, as the load increases,the background noise 1362 also increases. After completing this test,the cutter was visually examined. Although there were no visual signs ofany damage on the top PCD surface of the cutter, the acoustic sensor diddetect acoustic events occurring within the cutter. Thus, the acousticsensor is able to detect minimal damage occurring to the cutters onceexposed to a load even though the damage is not visible.

FIG. 14 shows a graphical cutter acoustic emission and loadingrepresentation for a cutter experiencing a load of up to about fortykilonewtons in accordance with an exemplary embodiment of the presentinvention. The same cutter sample used in the tests represented in FIG.13 was used in the test represented in FIG. 14. Referring to FIG. 14,the cutter acoustic emission and loading representation 1400 includes atime axis 1410, a load axis 1420, and an acoustic emissions axis 1430.The time axis 1410 is represented by an x-axis and is provided withunits in the seconds times 5,000. Thus, to obtain the time period inseconds, the numerical value in the time axis 1410 is to be divided by5,000. The time axis 1410 can also be read as energy being delivered tothe sample. In other words, as more time passes, more total energy isexerted on the sample. The load axis 1420 is represented by a y-axis andis provided with units in the kilonewtons. The acoustic emissions axis1430 also is represented by the y-axis and is provided with units in themillivolts times ten. Thus, to obtain the voltage in millivolts, thenumerical value in the acoustic emissions axis 1430 is to be divided byten. A load curve 1440 and an acoustic emissions curve 1460 are bothillustrated on the cutter acoustic emission and loading representation1400. According to the load curve 1440, the load was increased from zerokilonewtons to forty kilonewtons at a constant rate 1442, or ramp uprate. The load was held at a peak load level 1443, or forty kilonewtonsin this example, for a period of time and then ramped down at a rampdown rate 1444, which is faster than the ramp up rate 1442. The acousticemissions curve 1460 represents the recorded signal from the acousticsensor. According to the acoustic emissions curve 1460, the acousticemissions recorded includes a background noise 1462 and one or moreacoustic events 1464. The acoustic events 1464 are shown as verticallines that significantly extend upwards from the background noise 1462.The height of each acoustic event 1464 above the background noise 1462is proportional to the amount of elastic energy released by eachcracking formation and/or propagation event by means of a calibrationconstant. As seen in FIG. 14, acoustic events 1464 did not occur withinthe cutter until the load reached or exceeded the previous load that wasexposed to this cutter. For example, this cutter previously experiencedloads up to thirty kilonewtons as described in FIG. 13. Thus, newacoustic events 1464 did not arise until the load reached and/orexceeded a threshold 1466, which was about thirty kilonewtons in thisexample, that was previously applied on to the cutter. Based upon theexperiments, it seems that to generate new cracks or to grow existingcracks in the cutter that were formed in a previous test run, a loadlevel equal to or higher than the previous peak load level 1343 is to beapplied.

FIG. 15A shows a graphical cutter acoustic emission and loadingrepresentation 1500 for a cutter manufacturer #1 cutter sample #1 cuttertype experiencing a load of up to about forty-five kilonewtons inaccordance with an exemplary embodiment of the present invention. FIG.15B shows a graphical cutter acoustic emission and loadingrepresentation 1550 for a cutter manufacturer #2 cutter sample #2 cuttertype experiencing a load of up to about thirty kilonewtons in accordancewith an exemplary embodiment of the present invention. Referring toFIGS. 15A and 15B, the cutter acoustic emission and loadingrepresentation 1500 includes an acoustic emission curve 1510 showing oneor more acoustic events 1520 occurring within the cutter manufacturer #1cutter sample #1 cutter type, while the cutter acoustic emission andloading representation 1550 includes an acoustic emission curve 1560showing one or more acoustic events 1570 occurring within the cuttermanufacturer #2 cutter sample #2 cutter type. There are significantlymore acoustics events 1520 and 1570 occurring within the cuttermanufacturer #2 cutter sample #2 cutter type than in the cuttermanufacturer #1 cutter sample #1 cutter type. Thus, different cuttertypes show different acoustic patterns within their respective acousticemissions curve. Based upon these results, a user can determine whichcutter type is tougher than another cutter type and can thereby rankcutters according to their toughness. In this case, the cuttermanufacturer #1 cutter sample #1 cutter type is tougher than the cuttermanufacturer #2 cutter sample #2 cutter type.

Based upon the experimental results shown in FIGS. 11-15, there are atleast several observations that can be made. First, the acoustic sensoris able to detect crack formation and crack growth within the diamondtable of the cutter as the indenter is being loaded and is able to sendsignals that are subsequently analyzable. Second, different cutter typesshow different acoustic event patterns and allow a user to rank thetoughness of the cutter when compared to another cutter. Third, althoughthere can be no visible damage that is detectable on the surface of thePDC table of the cutter after the test, the acoustic sensor is able todetect any non-visible damage occurring to the cutter.

FIG. 16 illustrates a flowchart of a method 1600 for analyzing datapoints received from the acoustic sensor, wherein the method includes aloop one method 1680 and a loop two method 1690 in accordance with anexemplary embodiment of the present invention. Although certain stepsare shown as proceeding in a particular order, the sequence of steps canbe varied without departing from the scope and spirit of the exemplaryembodiment. Also, although certain functions are performed in one ormore steps, the number of steps for performing that function can beincreased or decreased without departing from the scope and spirit ofthe exemplary embodiment.

Referring to FIG. 16, at step 1605, the method 1600 starts. From step1605, method 1600 proceed to step 1610. At step 1610, one or moreminimum threshold values above the background noise to qualify a datapoint as a possible acoustic event is determined. Upon completion ofstep 1610, method 1600 proceeds to step 1615 and step 1625, which canoccur simultaneously in certain exemplary embodiments. At step 1615, thebackground points delimiting the outer envelop of the background noiseis determined. At step 1625, the possible acoustic event points isdetermined based upon the one or more threshold values determined atstep 1610. Step 1615 and step 1625 are included in the loop one method1680, which is described in further detail below in conjunction withFIG. 17.

From step 1615, method 1600 proceeds to step 1620. At step 1620, thebackground points determined at step 1615 are interpolated to produce abackground noise function curve. From steps 1620 and 1625, method 1600proceeds to step 1630. At step 1630, actual acoustic event points aredetermined using the possible acoustic event points determined at step1680 and the background noise function curve determined at step 1620.From step 1630, method 1600 proceeds to step 1635. At step 1635, theamplitude and duration of each actual acoustic event point isdetermined. From step 1635, method 1600 proceeds to step 1640. At step1640, the area under each acoustic event point is calculated. From step1640, method 1600 proceeds to step 1645. At step 1645, the cumulativedistribution of the areas is compared to the actual test load for eachacoustic event point. A user can use this comparison to make adetermination as to the relative toughness of one cutter to anothercutter. This comparison allows the determination to be made using aquantitative and objective methods. The duration, amplitude, andfrequency of the acoustic event points and the corresponding level ofenergy, or load, delivered to the sample can be correlated directly withthe field impact performance of the PCD, or other hard or superhardmaterial, being tested. Method 1600 allows measurement of not only thesmallest amount of external work, or load, required to initiate somedamage but also allows measurement of the amount of additional work, orload, that has to be done to increase the damage level. After step 1645,method 1600 proceed to step 1650 where method 1600 is stopped.

FIG. 19 shows a graphical cutter acoustic emission representation 1900for a cutter experiencing a load in accordance with an exemplaryembodiment of the present invention. FIG. 20 shows a magnified view of aportion of a graphical cutter acoustic emission representation 2000 fora cutter experiencing a load in accordance with an exemplary embodimentof the present invention. FIG. 21 shows a cumulative distributionrepresentation 2100 for each actual acoustic event in accordance with anexemplary embodiment of the present invention. FIGS. 19-21 depict amajority of the steps illustrated in method 1600 of FIG. 16.

Referring to FIG. 19, the cutter acoustic emission representation 1900includes a time axis 1910 and an acoustic emissions axis 1930. The timeaxis 1910 is represented by an x-axis and is provided with units in theseconds times 5,000. Thus, to obtain the time period in seconds, thenumerical value in the time axis 1910 is to be divided by 5,000. Theacoustic emissions axis 1930 is represented by a y-axis and is providedwith units in the millivolts time ten. Thus, to obtain the voltage inmillivolts, the numerical value in the acoustic emissions axis 1930 isto be divided by ten. An acoustic emissions data 1960 is illustrated onthe cutter acoustic emission representation 1900. The acoustic emissionsdata 1960 represents the recorded signal from the acoustic sensor.According to the acoustic emissions data 1960, the acoustic emissionsdata recorded includes one or more background points 1962 and one ormore possible acoustic event points 1964. Referring to FIGS. 16 and 19and according to step 1615 and step 1625 of FIG. 16, the acousticemissions data 1960 is sorted to include background points 1962 andpossible acoustic event points 1964. The sorting of the acousticemissions data 1960 is performed using an algorithm that resides withindata recorder 590 (FIG. 5) according to one exemplary embodiment.However, the algorithm can be stored in another device in alternativeexemplary embodiments or is performed manually. Alternatively, othermethods known to people having ordinary skill in the art and having thebenefit of the present disclosure can be used to categorize the acousticemissions data 1960. As shown in FIG. 19, each background point 1962 ismarked with a circle and each possible acoustic event point 1964 ismarked with a square. There are some points that are not defined aseither a background point 1962 or a possible acoustic event point 1964.These markings are for illustrative purposes and is not meant to limitthe scope of exemplary embodiments of the present invention.

Referring to FIGS. 16 and 19 and according to step 1620 of FIG. 16, abackground noise function curve 1970 is interpolated using thedetermined background points 1962. According to one exemplaryembodiment, the background noise function curve 1970 is interpolatedusing a fourth degree polynomial; however, other degrees of polynomialcan be used to interpolate the background points 1962 without departingfrom the scope and spirit of the exemplary embodiment.

Referring to FIG. 20, a magnified portion of the graphical cutteracoustic emission representation 2000 is presented. According to thisfigure, each acoustic emissions data 1960, which includes the actualacoustic event points 2010, has a time duration 2020 that it occurs in.Additionally, each actual acoustic event point 2010, has an amplitude2030 that is measured vertically from the background noise functioncurve 1970 to the position where the actual acoustic event point 2010lies. Referring to FIGS. 16 and 20 and according to step 1635 of FIG.16, the amplitude 2030 and the time duration 2020 of the actual acousticevent point 2010 is calculated. Once the amplitude 2030 and the timeduration 2020 is determined, the area 2040 under each actual acousticevent point 2010 is calculated by multiplying the amplitude 2030 to thetime duration 2020. This step is accomplished in step 1640 of FIG. 16.According to some of the exemplary embodiments, the units for the area2040 is millivolt times seconds times 5,000; however, other units can beused without departing from the scope and spirit of the exemplaryembodiment.

Referring to FIG. 21, a cumulative distribution representation 2100 foreach actual acoustic event is presented. According to this figure, thecumulative distribution representation 2100 includes a load axis 2110and an acoustic emissions area axis 2130. The load axis 2110 isrepresented by an x-axis and is provided with units in the kilonewtons.The acoustic emissions area axis 2130 is represented by a y-axis and isprovided with units in the millivolts times seconds times fiftythousand. This is the area that is determined that lies under an actualacoustic event point. Thus, to obtain the area in millivolts timesseconds, the numerical value in the acoustic emissions area axis 2130 isto be divided by fifty thousand. Referring to FIGS. 16 and 21 andaccording to step 1645 of FIG. 16, the cumulative distribution of theareas, which is plotted along the acoustic emissions area axis 2130, iscompared to the actual test load, which is plotted along the load axis2110, for each actual acoustic event. The cumulative distributionrepresentation 2100 provides these comparisons for a cutter manufacturer#1 cutter sample #1 cutter plot 2150 and a cutter manufacturer #2 cuttersample #2 cutter plot 2160.

For example, in one of the three cutter manufacturer #1 cutter sample #1cutter plots 2150, there is an actual acoustic event point at abouttwenty-eight kilonewtons and at about 3550 millivolt times seconds times50,000, which is labeled as a Point A 2152. This means that there hasbeen a cumulative area of 3550 millivolt times seconds times 50,000which has occurred under all previous actual acoustic event points,including the area for the actual acoustic event point that occurred atabout a load of about twenty-eight kilonewtons. The next actual acousticevent point, Point B 2154, on that same curve occurs at about 32.5kilonewtons. The area under that actual acoustic event point is about650 millivolt times seconds times 50,000, which is not directly shown onthe cumulative distribution representation 2100. However, at about 32.5kilonewtons, there has been a cumulative area of about 4200 millivolttimes seconds times 50,000. Thus, about 4200 millivolt times secondstimes 50,000 minus about 3550 millivolt times seconds times 50,000 isequal to about 650 millivolt times seconds times 50,000. The hardercutter, or the one that is more intrinsically tougher, provides a curvethat has a less cumulative area for a given load. A cutter with a steepcurve with a lot of high amplitude actual acoustic event points is lessintrinsically tougher than a cutter with a less steep curve and fewerhigh amplitudes actual acoustic event points. Thus, according to thecumulative distribution representation 2100, a comparison between thecutter manufacturer #1 cutter sample #1 cutter plot 2150 and the cuttermanufacturer #2 cutter sample #2 cutter plot 2160 indicates that thecutter manufacturer #1 cutter sample #1 cutter is intrinsically tougherthan the cutter manufacturer #2 cutter sample #2 cutter. Also, accordingto FIG. 21, there are three curves that represent the cuttermanufacturer #1 cutter sample #1 cutter plot 2150 and two curves thatrepresent the cutter manufacturer #2 cutter sample #2 cutter plot 2160.These plots 2150 and 2160 illustrate that method 1600 (FIG. 16) has ahigh resolution so that variabilities within samples of the same groupare detectable. The method provided in FIG. 16 provides information to auser for ranking cutter toughnesses amongst other cutters in anobjective manner.

FIG. 17 illustrates a detailed flowchart of the loop one method 1680 ofFIG. 16 in accordance with an exemplary embodiment of the presentinvention. Referring to FIG. 17, at step 1705, the loop one method 1680starts. From step 1705, loop one method 1680 proceeds to step 1710. Atstep 1710, the first data point is read. Upon completion of step 1710,loop one method 1680 proceeds to step 1715, where the next data point isread. After step 1715, loop one method 1680 proceeds to step 1720. Atstep 1720, the difference between the two data points is calculated andcompared to a first tolerance value that is used to define an acousticevent. According to one exemplary embodiment, the first tolerance valueis about 0.5 millivolts. However, the first tolerance value can behigher or lower in other exemplary embodiments. If the differencebetween the two data points is not less than the first tolerance value,loop one method 1680 proceeds to step 1725. At step 1725, the second ofthe two data points is defined as a possible acoustic event point. Fromstep 1725, loop one method 1680 proceeds to step 1745, where loop onemethod 1680 determines whether there is another data point. If at step1745, it is determined that there is not another data point, loop onemethod 1680 proceeds to step 1750, where the loop one method 1680 stops.However, if at step 1745, it is determined that there is another datapoint, the loop one method 1680 proceeds back to step 1715.

If at step 1720, it is determined that the difference between the twodata points is less than the first tolerance value, the loop one method1680 proceeds to step 1730. At step 1730, the difference between the twodata points is compared to a second tolerance value. According to oneexemplary embodiment, the second tolerance value is about 0.01millivolts. However, the second tolerance value can be higher or lowerin other exemplary embodiments. If the difference between the two datapoints is not less than the second tolerance value, loop one method 1680proceeds back to step 1715 and the second data point is not defined.However, if the difference between the two data points is less than thesecond tolerance value, loop one method 1680 proceeds to step 1735.

At step 1735, it is determined whether the difference between the twodata points is negative and has been negative for less than “z” times ina row or whether the difference is positive and has been positive forless than “u” times in a row. According to one exemplary embodiment, the“z” is two and the “u” is three. However, either or both the “u” valueand the “z” value can be higher or lower in other exemplary embodiments.If it is not true that the difference between the two data points isnegative and has been negative for less than “z” times in a row or ispositive and has been positive for less than “u” times in a row, thenthe loop one method 1680 proceeds back to step 1715 and the second datapoint is not defined. However, if the difference between the two datapoints is negative and has been negative for less than “z” times in arow or is positive and has been positive for less than “u” times in arow, then the loop one method 1680 proceeds to step 1740.

At step 1740, the second of the two data points is defined as abackground boundary point. From step 1740, the loop one method 1680proceeds to step 1745, where it is determined whether there is anotherdata point. The loop one method 1680 continues until step 1750 isreached pursuant to the steps described above. Thus, the loop one method1680 provides a method for determining which data points should bedefined as a possible acoustic event point, a background boundary point,or not defined as either type of point.

FIG. 18 illustrates a detailed flowchart of the loop two method 1690 ofFIG. 16 in accordance with an exemplary embodiment of the presentinvention. Referring to FIG. 18, at step 1805, the loop two method 1690starts. From step 1805, loop two method 1690 proceeds to step 1810. Atstep 1810, a background noise function curve is created using thebackground boundary points. Upon completion of step 1810, loop twomethod 1690 proceeds to step 1815, where the first possible acousticevent point is read. After step 1815, loop two method 1690 proceeds tostep 1820. At step 1820, the difference between the possible acousticevent point and the background noise function curve is calculated anddetermined whether this difference is greater than a third tolerancevalue that is used to define an actual acoustic event point. Accordingto one exemplary embodiment, the third tolerance value is about 0.08millivolts. However, the third tolerance value can be higher or lower inother exemplary embodiments. If the difference between the possibleacoustic event point and the background noise function curve is notgreater than the third tolerance value, loop two method 1690 proceeds tostep 1825. At step 1825, the next possible acoustic event point is readand the loop two method 1690 proceeds back to step 1820. However, if thedifference between the possible acoustic event point and the backgroundnoise function curve is greater than the third tolerance value, loop twomethod 1690 proceeds to step 1830.

At step 1830, the amplitude, the duration, and the area between theactual acoustic event point and the background noise function curve arecalculated From step 1830, the loop two method 1690 proceeds to step1840. At step 1840, it is determined whether there is another possibleacoustic event point. If there is another possible acoustic event point,the loop two method 1690 proceeds back to step 1825, where the loop twomethod 1690 continues. However, at step 1840, if there is not anotherpossible acoustic event point, the loop two method 1690 proceeds to step1845, where the loop two method 1690 stops. Thus, the loop two method1690 provides a method for determining which data points should bedefined as an actual acoustic event point and then calculates the areafor each defined acoustic event point.

FIG. 22 illustrates a block diagram of the processor 1020 of FIG. 10 inaccordance with an exemplary embodiment. As previously mentioned, themethod for performing one or more steps illustrated in FIGS. 16-18 isperformed within the processor 1020. However, in certain other exemplaryembodiments, these methods are performed manually or a combination ofmanually and within a processor. The processor 1020 is located withinthe data recorder 590, or a computer system. Although one processor 1020is shown, multiple processors can be used without departing from thescope and spirit of the exemplary embodiments. Processor 1020 includesone or more processor engines 2200.

The processor engines 2200 include an acoustic data gathering engine2210, a background points determination engine 2220, a possible acousticevent points determination engine 2230, a background noise functioncurve interpolation engine 2240, an actual acoustic event pointsdetermination engine 2250, an actual acoustic event area calculationengine 2260, and a cumulative area and load curve engine 2270. Althoughseven engines are included within the processor engines 2200, the numberof engines can be greater or fewer in other exemplary embodiments.Additionally, one or more of these previously mentioned processorengines 2200 can be combined into fewer processor engines 2200 orseparated into additional processor engines 2200 without departing fromthe scope and spirit of the exemplary embodiments.

The acoustic data gathering engine 2210 gathers data from at least theacoustic sensor, which includes background points and possible acousticevent points. The acoustic data gathering engine 2210 also gathers datafrom the load, in some exemplary embodiments, so that correspondingbackground points and possible acoustic event points are related to agiven load. The background points determination engine 2220 evaluatesthe data obtained from the acoustic sensor and determines whether thedata point is a background point. The background points determinationengine 2220 performs step 1615 of FIG. 16. The possible acoustic eventpoints determination engine 2230 evaluates the data obtained from theacoustic sensor and determines whether the data point is a possibleacoustic event point. The possible acoustic event points determinationengine 2230 performs step 1625 of FIG. 16. The background pointsdetermination engine 2220 and the possible acoustic event pointsdetermination engine 2230 run simultaneously with one another, but canrun independently from one another in some alternative exemplaryembodiments.

The background noise function curve interpolation engine 2240 generatesa background noise function curve using the background points that werepreviously determined. The background noise function curve interpolationengine 2240 performs step 1620 of FIG. 16. The actual acoustic eventpoints determination engine 2250 determines actual acoustic event pointsusing the possible acoustic event points that were previously determinedand the background noise function curve. The actual acoustic eventpoints determination engine 2250 performs step 1630 of FIG. 16. Once theactual acoustic event points are determined, the actual acoustic eventarea calculation engine 2260 determines the area formed between theactual acoustic event point and the background noise function curve. Theactual acoustic event area calculation engine 2260 performs step 1635and step 1640 of FIG. 16. The cumulative area and load curve engine 2270compares the cumulative distribution of the areas to the actual testload for each actual acoustic event point. The cumulative area and loadcurve engine 2270 performs step 1645 of FIG. 16. Although the processorengines 2200 are located in the processor 1020 in some exemplaryembodiments, the processor engines 2200 can reside in a storage mediumincluding, but not limited to, one or more hard drives, a USB drive, acompact disc, a digital video disc, or any other storage device known ornot yet known to people having ordinary skill in the art.

Although processor engines 2200 are described in the exemplaryembodiments, the instructions for determining the toughness of thecutter can be provided in a software that resides within the storagemedium 1040 (FIG. 10). The software includes modules and/or code thatare similar to the processor engines 2200 described above.

FIG. 23 shows a rock sample 2300 that is testable within the acousticemission testing systems 500 and 900 of FIGS. 5 and 9, respectively, inlieu of the cutter 100 of FIG. 1 in accordance with an exemplaryembodiment. Referring to FIGS. 5, 6, 9, and 23, the rock sample 2300replaces the cutter 100 in the acoustic emission testing system 500 orthe acoustic emission testing system 900. The testing method andanalysis of the results are similar to those methods and analysisdescribed above and provides information relating to the unconfinedcompressive strength and/or toughness of the rock sample 2300.

The rock sample 2300 is cylindrically shaped, which is similar to thecutter 100. The rock sample includes a first planar surface 2310 at oneend of the rock sample 2300, a second planar surface 2320 at an opposingend of the rock sample, and a circumferential surface 2330 extendingfrom the first surface 2310 to the second surface 2320. However, inalternative exemplary embodiments, the rock sample 2300 is shaped inother geometric or non-geometric shapes, such as cube-shaped. In certainexemplary embodiments, the shape of the rock sample 2300 is a repeatableshape such that multiple rock samples 2300 are formed with asubstantially similar shape; thereby allowing the test results to becomparable.

FIG. 24 shows the acoustic emission testing device 505 of FIG. 5inserted within a pressurizable chamber 2410 in accordance with anexemplary embodiment. The pressure within the pressurizable chamber 2410is variable in a controllable and measurable manner. The pressure withinthe pressurizable chamber 2410 is variable from zero psi to about 40000psi in some exemplary embodiments; however, the range of pressures canbe higher or lower in other exemplary embodiments. In this exemplaryembodiments, other components, including the sensor 570 and the indenter550, are capable of withstanding the pressures formed within thepressurizable chamber 2410. According to these exemplary embodiments,the rock confined compressive strength and toughness are measurable atdifferent levels of hydrostatic pressures, thereby providing vitalinformation of the rock properties at different depths below the earthsurface. The information collected is usable to improve the knowledge ofrock failing mechanisms and also lead to new theories and rock solidmechanic models. The information collected also is usable to confirmother known theories not yet proven. Although the pressurizable chamber2410 is one method for testing the hard or superhard material 100, suchas the rock sample 2300, under pressure, other mechanisms for providingpressures on the hard or superhard material 100 can be used, such asusing high strength binding rings assembled together and around the hardor superhard material 100, in alternative exemplary embodiments.

The knowledge of the UCS and the toughness of the rock samples 2300 areusable by designers to create new and innovative bit designs havingsuperior performance and/or to develop a new bit design procedure whichincorporates the UCS value and the K_(1C) value. The informationobtained from the rock samples 2300 is usable to calibrate geoscienceand/or geomechanics software and tools.

Although some exemplary embodiments of the invention have beendescribed, alternative exemplary embodiments include the use of heatingthe hard or superhard material 100. This heating of the hard orsuperhard material 100 occurs at either or a combination of before,during, and/or after the application of the load onto the hard orsuperhard material 100. The heat is supplied in any one of a number ofways known to people having ordinary skill in the art, which include,but is not limited to, flame, laser, infrared, and/or heated liquid.

FIG. 25 shows a cross-sectional view of an acoustic emission testingsystem 2500 in accordance with an exemplary embodiment of the presentinvention. Referring to FIG. 25, the acoustic emission testing system2500 includes an acoustic emission testing device 2505 communicablycoupled to an analog-to-digital converter 2592, which is communicablycoupled to a data recorder 2590. According to some exemplaryembodiments, the analog-to-digital converter 2592 is optional. Theacoustic emission testing device 2505 includes a pressurizable chamber2510, a rock sample 2580, one or more acoustic sensors 2570, a firstbarrier 2530, a second barrier 2540, and a drain pipe 2595. In someexemplary embodiments, the acoustic emission testing device 2505 alsoincludes one or more couplings 2594 and a drain pipe pressure controlvalve 2597. Although the rock sample 2580 is depicted in the exemplaryembodiment, other types of porous samples can be used in lieu of therock sample 2580 according to other alternative exemplary embodiments.

The pressurizable chamber 2510 is cylindrically shaped and forms acavity 2512 therein. However, according to other exemplary embodiments,the pressurizable chamber 2510 is shaped in some other geometric shape,such as a cube-shape, or non-geometric shape. The pressure within thepressurizable chamber 2510 is variable in a controllable and measurablemanner. The pressure within the pressurizable chamber 2510 is variablefrom zero psi to about 40000 psi in some exemplary embodiments; however,the range of pressures can be higher or lower in other exemplaryembodiments. The pressurizable chamber 2510 includes a base 2514 and asidewall 2516 extending substantially perpendicular around the perimeterof the base 2514. In some alternative exemplary embodiments, thesidewall 2516 extends substantially perpendicular from the base 2514 ata position that is within the perimeter of the base 2514. Thepressurizable chamber 2510 is fabricated from steel; however, accordingto other exemplary embodiments, the pressurizable chamber 2510 isfabricated from any metal, metal alloy, polymer, wood, or other suitablematerial known to people having ordinary skill in the art that iscapable of withstanding at least a second pressure (P₀) 2527, which isdescribed in further detail below. In certain exemplary embodiments, thesuitable material is capable of being machined or molded and is capableof propagating sound. In certain exemplary embodiments, the suitablematerial is capable of propagating sound at a speed of about 1kilometers per second or higher.

The cavity 2512 is formed within the pressurizable chamber 2510 and issized to receive the entire rock sample 2580, or some other hard orsuperhard material. The cavity 2512 is sized larger in diameter than thediameter of the rock sample 2580, thereby allowing the rock sample 2580to easily and freely fit within the cavity 2512. The cavity 2512 iscircular in shape, but is any other geometric or non-geometric shape inother exemplary embodiments. The cavity 2512 is formed by machining thepressurizable chamber 2510 or molding the pressurizable chamber 2510 tohave the cavity 2512 formed therein. Alternatively, the cavity 2512 isformed using other methods known to people having ordinary skill in theart. In certain exemplary embodiments, the cavity 2512 is formed in amanner to ensure that the rock sample 2580 is properly aligned in thesame manner each time the rock sample 2580 is inserted within the cavity2512. For example, the base 2514 can be keyed to receive the rock sample2580 in a desired position. For example, the base 2514 includes one ormore protrusions (not shown) and/or one or more indentations (not shown)in certain exemplary embodiments.

The rock sample 2580 is a porous material. According to some exemplaryembodiments, the rock sample 2580 is formed from a sample of rockobtained from within a drill hole, or wellbore, located at some depthwithin the wellbore and at a confining pressure. Some examples of rocksamples 2580 include, but are not limited to, coal, chalk, shale,limestone, sandstone, all geological formations that include gas or oil,and other known porous rocks. The rock sample 2580 is substantiallycylindrical in shape, but can be shaped into other geometric shapes,such as substantially cube-shaped, or non-geometric shapes. The rocksample 2580 includes a top surface 2582, a bottom surface 2584, and asidewall 2586 extending from the top surface 2582 to the bottom surface2584. The top surface 2582 and the bottom surface 2584 are substantiallyparallel to one another; however, according to other exemplaryembodiments, the top surface 2582 and the bottom surface 2584 are notparallel to one another. The sidewall 2586 extends substantiallyperpendicular to both the top surface 2582 and the bottom surface 2584;however, in certain exemplary embodiments, the sidewall 2586 is notperpendicular to at least one of the top surface 2582 and the bottomsurface 2584. According to some exemplary embodiments, the sidewall 2586is arcuate; however, according to some other exemplary embodiments, atleast some portions of the sidewall 2586 includes one or more planarsurfaces (not shown). In these exemplary embodiments, these planarsurfaces facilitate acoustic sensors 2570 being coupled to the rocksample 2580. The rock sample 2580 is inserted within the cavity 2512 sothat the bottom surface 2584 is adjacent to the base 2514. According tosome exemplary embodiments, the rock sample 2580 is positionedsubstantially in the center of the cavity 2512; however, the rock sample2580 can be positioned off-center of the cavity 2512 in other exemplaryembodiments.

The acoustic sensor 2570 is a piezoelectric sensor that is positionedalong the sidewall 2586 of the rock sample 2580. However, the acousticsensor 2570 can be any other device type known to people having ordinaryskill in the art, wherein the device is capable of detecting acoustictransmissions. Additionally, according to some exemplary embodiments,the acoustic sensor 2570 is positioned along the exterior portion of thesidewall 2516 of the pressurizable chamber 2510. According to someexemplary embodiments, the acoustic sensor 2570 is sized so that it iscapable of being placed on the arcuate portion of the sidewall 2586,2516. In other exemplary embodiments, the acoustic sensor 2570 is placedon a planar portion (not shown) of the sidewall 2586, 2516. The acousticsensor 2570 detects elastic wave signals formed in the rock sample 2580,which then converts the elastic waves signal to a voltage signal so thatthe data can be recorded and subsequently analyzed.

The acoustic sensor 2570 is communicably coupled to the data recorder2590, via the analog-to-digital converter 2592 in certain exemplaryembodiments, so that the voltage signal derived from the elastic wavesoccurring within the rock sample 2580 can be stored and subsequentlyanalyzed. The data recorder 2590 is similar to the data recorder 590(FIG. 5) and will not be discussed in detail again. The data recorder2590 also is set-up similarly to the set-up of data recorder 590 (FIG.5). In some exemplary

According to the exemplary embodiment illustrated in FIG. 25, there arefour acoustic sensors 2570 coupled to the rock sample 2580. However, thenumber of acoustic sensors 2570 ranges from one acoustic sensor 2570 toany number of acoustic sensors 2570. The acoustic sensors 2570 are ableto detect the intensity of acoustic events occurring on or within therock sample 2580 with respect to time and space. Thus, the location ofthe acoustic events and the direction in which the cracks arepropagating within the rock sample 2580 are determinable. According tosome examples, at least one or more acoustic sensors 2570 are positionedat different elevational heights along the sidewall 2586. In oneexample, three acoustic sensors 2570 are coupled to the rock sample 2580at different elevational heights along the sidewall 2586. A firstacoustic sensor 2570 detects the intensity of the acoustic eventoccurring within the rock sample 2580 at a first time period anddetermines the location of the acoustic event occurring within the rocksample 2580 along a first axis, or x-axis. A second acoustic sensor 2570detects the intensity of the acoustic event occurring within the rocksample 2580 at the first time period and determines the location of theacoustic event occurring within the rock sample 2580 along a secondaxis, or y-axis. A third acoustic sensor 2570 detects the intensity ofthe acoustic event occurring within the rock sample 2580 at the firsttime period and determines the location of the acoustic event occurringwithin the rock sample 2580 along a third axis, or z-axis. The acousticsensors 2570 perform the same analysis at a second time period, a thirdtime period, and so forth. Using the speed of sound known within therock sample 2580, data from the three acoustic sensors 2570 provideinformation for determining the intensity of the acoustic eventoccurring within the rock sample 2580, the location of the acousticevent occurring within the rock sample 2580, and the direction in whichthe acoustic event is propagating within the rock sample 2580. In theembodiments where the acoustic sensors 2570 are positioned along thepressurizable chamber's sidewall 2516, the speed of sound through afirst fluid 2521 and the distance between the respective acoustic sensor2570 and the rock sample's sidewall 2586 also are used in thedeterminations. If fewer acoustic sensors 2570 are used, one or moreaxes are lost for determining where the acoustic event is occurringwithin the rock sample 2580 along those axes. Each acoustic sensor 2570represents an axis. When greater than three acoustic sensors 2570 areused, the measurements provide more precise determinations for locatingthe acoustic events occurring within the rock sample 2580. The data fromthe three acoustic sensors 2570 are used to triangulate the location ofthe acoustic event.

The first barrier 2530 is substantially disc-shaped and includes anopening 2532 extending therethough. The opening 2532 is substantiallypositioned centrally within the first barrier 2530 and is sized forinserting at least the top surface 2582 within the opening 2532. In someexemplary embodiments, the opening 2532 is used to properly position therock sample 2580 in the pressurizable chamber 2510. In some exemplaryembodiments, the top surface 2582 and at least a portion of the rocksample's sidewall 2586 is inserted through the opening 2532. The opening2532 is shaped similarly to the shape of at least a portion of across-sectional portion of the rock sample's sidewall 2586. Although thefirst barrier 2530 is substantially disc-shaped, the shape can be anyother geometric shape or non-geometric shape that is substantiallysimilar to at least a portion of the cross-sectional shape of the cavity2512. The first barrier 2530 is fixedly coupled to the interior portionof the sidewall 2516 of the pressurizable chamber 2510, thereby dividingthe cavity 2512 into a first chamber 2520 and a second chamber 2525. Thefirst barrier 2530 is coupled to the sidewall 2516 using welding or anyother methods known to people having ordinary skill in the art. The weldor any other device used for attaching the first barrier 2530 to thepressurizable chamber's sidewall 2516 is capable of withstandingpressures of at least the second pressure 2527. The first barrier 2530is fabricated using a metal, metal alloy, polymer, or any other suitablematerial capable of withstanding pressures of up to at least the secondpressure 2527. A first seal 2534 is positioned about the perimeter ofthe opening 2532 and provides a pressure seal with the rock sample'ssidewall 2586. The first seal 2534 is a rubber gasket or any othersuitable material known to people having ordinary skill in the art. Thepressure within the first chamber 2520 is a first pressure (P₁) 2522which can be different than the second pressure 2527 within the secondchamber 2525 during testing, which is described in further detail below.Each of the first pressure 2522 and the second pressure 2527 isvariable. Thus, a portion of the rock sample 2580 is exposed to thefirst pressure 2522 while another portion of the rock sample 2580 isexposed to the second pressure 2527 during testing.

Within the first chamber 2520, the first fluid 2521 is placed. The firstfluid 2521 fills up the entire first chamber 2520 in some exemplaryembodiments; however, in other exemplary embodiments, the first fluid2521 fills a portion of the first chamber 2520. The first fluid 2521 iswater. However, other types of fluid having similar properties can beused as the first fluid 2521 in other exemplary embodiments. In someexemplary embodiments, the first fluid 2521 includes sand particles orother similar particle types.

The second barrier 2540 also is substantially disc-shaped and includes asecond seal 2542 around the perimeter of the second barrier 2540.Although the second barrier 2540 is substantially disc-shaped, the shapecan be any other geometric shape or non-geometric shape that issubstantially similar to at least a portion of the cross-sectional shapeof the cavity 2512. The second barrier 2540 is positioned near the topportion of the pressurizable chamber 2510 within the cavity 2512 and ismovably coupled to the interior portion of the sidewall 2516 of thepressurizable chamber 2510. The second barrier 2540 forms a portion ofthe second chamber 2525. The second seal 2542 provides a pressure sealbetween the second barrier 2540 and the pressurizable chamber's sidewall2516. The second seal 2542 is a rubber gasket or any other suitablematerial known to people having ordinary skill in the art. The secondbarrier 2540 thereby provides a means for varying the second pressure2527 within the second chamber 2525. An external force 2502 is appliedon the second barrier 2540 which moves the second barrier 2540 closer tothe first barrier 2530. As the second barrier 2540 moves closer to thefirst barrier 2520, the second pressure 2527 increases, and as thesecond barrier 2540 moves further away from the first barrier 2520, thesecond pressure 2527 decreases. The external pressure 2502 is providedby a piston 2503 in some exemplary embodiments; however, the externalforce 2502 can be provided by any other known methods and/or devices.The second barrier 2540 is fabricated using a metal, metal alloy,polymer, or any other suitable material capable of withstandingpressures of up to at least the second pressure 2527 and/or the externalforce 2502, whichever is greater.

Within the second chamber 2525, a second fluid 2526 is placed. Thesecond fluid 2526 fills up the entire second chamber 2525 in someexemplary embodiments; however, in other exemplary embodiments, thesecond fluid 2526 fills a portion of the second chamber 2525. The secondfluid 2526 is water. However, other types of fluid having similarproperties can be used as the second fluid 2526 in other exemplaryembodiments. In some exemplary embodiments, the second fluid 2526includes sand particles or other similar particle types. According tosome exemplary embodiments, the second fluid 2526 is the same as thefirst fluid 2521; however, the second fluid 2526 can be different than,but similar in properties to, the first fluid 2521 in other exemplaryembodiments. As the second pressure 2527 in the second chamber 2525increases above the first pressure 2522 in the first chamber 2520, thesecond fluid 2526 flows from the second chamber 2525 into the rocksample 2580 and out into the first chamber 2520. As the second pressure2527 increases, acoustic events, or cracks, form in the rock sample2580. In the exemplary embodiments where sand particles are included inthe second fluid 2526, the sand particles can enter into the cracksformed within the rock sample 2580 and become lodged therein as toprevent the cracks from closing when the second pressure 2527 isdecreased.

As the second pressure 2527 increases and the second fluid 2526 flowsinto the first chamber 2520 through the rock sample 2580, the firstpressure 2522 increases. To maintain the first pressure 2522 constant orsubstantially constant, a drain pipe 2595 is coupled to the interior ofthe first chamber 2520 and through the base 2514 to allow the firstfluid 2521 and/or the second fluid 2526 that is present within the firstchamber 2520 to exit the first chamber 2520. The drain pipe 2595 isfabricated from a metal, metal alloy, polymer, or other suitablematerial capable of withstanding the first pressure 2522. In certainexemplary embodiments, the drain pipe pressure control valve 2597 isinstalled at a location along the drain pipe 2595 and is configured tobe opened and closed, either automatically or manually, to maintain thefirst pressure 2522 at a substantially constant pressure during thetesting process. In alternative exemplary embodiments, the drain pipe2595 is coupled to the interior of the first chamber 2520 through thesidewall 2516.

The operation of the acoustic emission testing system 2500 is describedwhile referring to FIG. 25. Once the acoustic emission testing system2500 is configured according to the description provided above, thedrain pipe control valve 2597 is set to maintain the pressure in thefirst chamber 2520 at the first pressure 2522. The first pressure 2522is determined to be the rock confining pressure, which is the pressureat which the rock sample 2580 was exposed to while in the wellbore. Theexternal force 2502 exerted onto the second barrier 2540 is increased,thereby pushing the second barrier 2540 closer towards the first barrier2530. This movement of the second barrier 2540 compresses the secondfluid 2526, thereby increasing the second pressure 2527 within thesecond chamber 2525. The second pressure 2527 increases to a value abovethe first pressure 2522 and is ramped up so that acoustic events, orcracking, occurs on or within the rock sample 2580. The second pressure2527 is continuously ramped up until the second pressure 2527 reaches athreshold pressure, which is where extensive acoustic events occurwithin the rock sample 2580. Once the second pressure 2527 increasesabove the first pressure 2522, the second fluid 2526 passes through theporous rock sample 2580 and enters into the first chamber 2520. Thefirst pressure 2522 would typically increase due to the second fluid2526 entering the first chamber 2520; however, the drain pipe controlvalve 2597 maintains the first pressure 2522 substantially constant andallows the first fluid 2521 and/or the second fluid 2526 that hasentered into the first chamber 2520 to exit the first chamber 2520through the pipe drain 2595. This threshold pressure that is reached isthe pressure that is to be generated in the wellbore for fracing therock at that confining pressure. During the testing procedure, theacoustic events are measured according to the descriptions providedabove. Additionally, the location of the acoustic events aredeterminable by people having ordinary skill in the art having thebenefit of the present disclosure. Moreover, the direction in which theacoustic events are propagating also are determinable by people havingordinary skill in the art having the benefit of the present disclosure.The acoustic sensors 2570 obtain data when the second pressure 2627 isincreased. Additionally, in some exemplary embodiments, the acousticsensors 2570 also obtain data when the second pressure 2627 is decreasedafter reaching the threshold pressure. Although not illustrated, thefirst pressure 2522 and the second pressure 2527 are monitored.According to some exemplary embodiments, the second pressure 2527 isrecorded.

FIG. 26 shows a cross-sectional view of an acoustic emission testingsystem 2600 in accordance with another exemplary embodiment of thepresent invention. Referring to FIG. 26, the acoustic emission testingsystem 2600 includes an acoustic emission testing device 2605communicably coupled to an analog-to-digital converter 2592, which iscommunicably coupled to a data recorder 2590. According to someexemplary embodiments, the analog-to-digital converter 2592 is optional.The acoustic emission testing device 2605 includes a pressurizablechamber 2610, a rock sample 2680, one or more acoustic sensors 2570, acover 2630, and the drain pipe 2595. In some exemplary embodiments, theacoustic emission testing device 2605 also includes one or morecouplings 2594 and the drain pipe pressure control valve 2597. Althoughthe rock sample 2680 is depicted in the exemplary embodiment, othertypes of porous samples can be used in lieu of the rock sample 2680according to other alternative exemplary embodiments. Since theanalog-to-digital converter 2592, the data recorder 2590, the acousticsensors 2570, the drain pipe 2595, the couplings 2594, and the drainpipe pressure control valve 2597 have been previously described indetail with respect to FIG. 25, these components are not described indetail again with respect to FIG. 26.

The pressurizable chamber 2610 is cylindrically shaped and forms acavity 2612 therein. However, according to other exemplary embodiments,the pressurizable chamber 2610 is shaped in some other geometric shape,such as a cube-shape, or non-geometric shape. The pressure within thepressurizable chamber 2610 is variable in a controllable and measurablemanner. The pressure within the pressurizable chamber 2610 is variablefrom zero psi to about 40000 psi in some exemplary embodiments; however,the range of pressures can be higher or lower in other exemplaryembodiments. The pressurizable chamber 2610 includes a base 2614 and asidewall 2616 extending substantially perpendicular around the perimeterof the base 2614. In some alternative exemplary embodiments, thesidewall 2616 extends substantially perpendicular from the base 2614 ata position that is within the perimeter of the base 2614. According tosome exemplary embodiments, the top portion of the sidewall 2616includes threads 2617 for receiving and coupling with the cover 2630.However, in other exemplary embodiments, the cover 2630 is sealablycoupled to the top portion of the sidewall 2616 using other methodsknown to people having ordinary skill in the art, such as usingfasteners and using welds. The pressurizable chamber 2610 is fabricatedfrom steel; however, according to other exemplary embodiments, thepressurizable chamber 2610 is fabricated from any metal, metal alloy,polymer, wood, or other suitable material known to people havingordinary skill in the art that is capable of withstanding at least asecond pressure (P₀) 2627, which is described in further detail below.In certain exemplary embodiments, the suitable material is capable ofbeing machined or molded and is capable of propagating sound. In certainexemplary embodiments, the suitable material is capable of propagatingsound at a speed of about 1 kilometers per second or higher.

The cavity 2612 is formed within the pressurizable chamber 2610 and issized to receive the entire rock sample 2680, or some other hard orsuperhard material. The cavity 2612 is sized larger in diameter than thediameter of the rock sample 2680, thereby allowing the rock sample 2680to easily and freely fit within the cavity 2612. The cavity 2612 iscircular in shape, but is any other geometric or non-geometric shape inother exemplary embodiments. The cavity 2612 is formed by machining thepressurizable chamber 2610 or molding the pressurizable chamber 2610 tohave the cavity 2612 formed therein. Alternatively, the cavity 2612 isformed using other methods known to people having ordinary skill in theart. In certain exemplary embodiments, the cavity 2612 is formed in amanner to ensure that the rock sample 2680 is properly aligned in thesame manner each time the rock sample 2680 is inserted within the cavity2612. For example, the base 2614 can be keyed to receive the rock sample2680 in a desired position. For example, the base 2614 includes one ormore protrusions and/or one or more indentations in certain exemplaryembodiments.

The rock sample 2680 is a porous material. According to some exemplaryembodiments, the rock sample 2680 is formed from a sample of rockobtained from within a drill hole, or wellbore, located at some depthwithin the wellbore and at a confining pressure. Some examples of rocksamples 2680 include, but are not limited to, coal, chalk, shale,limestone, sandstone, all geological formations that include gas or oil,and other known porous rocks. The rock sample 2680 is substantiallycylindrical in shape, but can be shaped into other geometric shapes,such as substantially cube-shaped, or non-geometric shapes. The rocksample 2680 includes a top surface 2682, a bottom surface 2684, and asidewall 2686 extending from the top surface 2682 to the bottom surface2684. The top surface 2682 and the bottom surface 2684 are substantiallyparallel to one another; however, according to other exemplaryembodiments, the top surface 2682 and the bottom surface 2684 are notparallel to one another. The sidewall 2686 extends substantiallyperpendicular to both the top surface 2682 and the bottom surface 2684;however, in certain exemplary embodiments, the sidewall 2686 is notperpendicular to at least one of the top surface 2682 and the bottomsurface 2684. According to some exemplary embodiments, the sidewall 2686is arcuate; however, according to some other exemplary embodiments, atleast some portions of the sidewall 2686 includes one or more planarsurfaces (not shown). In these exemplary embodiments, these planarsurfaces facilitate acoustic sensors 2570 being coupled to the rocksample 2680.

The rock sample 2680 also includes an opening 2681 extending from thetop surface 2682 to the bottom surface 2684. The opening 2681 ispositioned centrally through the rock sample 2680; however, in otherexemplary embodiments, the opening 2681 can be positioned off-centeredthrough the rock sample 2680. In alternative exemplary embodiments, theopening 2681 extends toward the bottom surface 2684 but does not extendthrough the bottom surface 2684. The rock sample 2680 is inserted withinthe cavity 2612 so that the bottom surface 2684 is adjacent to the base2614. According to some exemplary embodiments, the rock sample 2680 ispositioned substantially in the center of the cavity 2612; however, therock sample 2680 can be positioned off-center of the cavity 2612 inother exemplary embodiments.

The acoustic sensor 2570 has been previously described and will not bedescribed in detail for the sake of brevity. One or more acousticsensors are positioned along the sidewall 2686 of the rock sample 2680.According to some exemplary embodiments, the one or more acousticsensors 2570 are positioned along the exterior portion of the sidewall2616 of the pressurizable chamber 2610. The acoustic sensor 2570 detectselastic wave signals formed in the rock sample 2680, which then convertsthe elastic waves signal to a voltage signal so that the data can berecorded and subsequently analyzed.

The acoustic sensor 2570 is communicably coupled to the data recorder2590, via the analog-to-digital converter 2592 in certain exemplaryembodiments, so that the voltage signal derived from the elastic wavesoccurring within the rock sample 2680 can be stored and subsequentlyanalyzed. The data recorder 2590 and the analog-to-digital converter2592, along with their respective set-ups, have been previouslydescribed and will not be described in detail for the sake of brevity.In the example where the acoustic sensor 2570 is placed on the rocksample 2680, the first cable 2591 is routed from within thepressurizable chamber 2610 to an area outside the pressurizable chamber2610 through the coupling 2594, which also has been previously describedabove and therefore will not be repeated for the sake of brevity.

According to the exemplary embodiment illustrated in FIG. 26, there arethree acoustic sensors 2570 shown to be coupled to the rock sample 2680.However, the number of acoustic sensors 2570 ranges from one acousticsensor 2570 to any number of acoustic sensors 2570. The acoustic sensors2570 is able to detect the intensity of acoustic events occurring on orwithin the rock sample 2680 with respect to time and space. Thus, thelocation of the acoustic events and the direction in which the cracksare propagating within the rock sample 2680 are determinable. Accordingto some examples, at least one or more acoustic sensors 2570 arepositioned at different elevational heights along the sidewall 2686. Inone example, three acoustic sensors 2570 are coupled to the rock sample2680 at different elevational heights along the sidewall 2586. A firstacoustic sensor 2570 detects the intensity of the acoustic eventoccurring within the rock sample 2680 at a first time period anddetermines the location of the acoustic event occurring within the rocksample 2680 along a first axis, or x-axis. A second acoustic sensor 2570detects the intensity of the acoustic event occurring within the rocksample 2680 at the first time period and determines the location of theacoustic event occurring within the rock sample 2680 along a secondaxis, or y-axis. A third acoustic sensor 2570 detects the intensity ofthe acoustic event occurring within the rock sample 2680 at the firsttime period and determines the location of the acoustic event occurringwithin the rock sample 2680 along a third axis, or z-axis. The acousticsensors 2570 perform the same analysis at a second time period, a thirdtime period, and so forth. Using the speed of sound known within therock sample 2680, data from the three acoustic sensors 2570 provideinformation for determining the intensity of the acoustic eventoccurring within the rock sample 2680, the location of the acousticevent occurring within the rock sample 2680, and the direction in whichthe acoustic event is propagating within the rock sample 2680. In theembodiments where the acoustic sensors 2570 are positioned along thepressurizable chamber's sidewall 2616, the speed of sound through afirst fluid 2621 and the distance between the respective acoustic sensor2570 and the rock sample's sidewall 2686 also are used in thedeterminations. If fewer acoustic sensors 2570 are used, one or moreaxes are lost for determining where the acoustic event is occurringwithin the rock sample 2680 along those axes. Each acoustic sensor 2570represents an axis. When greater than three acoustic sensors 2570 areused, the measurements provide more precise determinations for locatingthe acoustic events occurring within the rock sample 2680. The data fromthe three acoustic sensors 2570 are used to triangulate the location ofthe acoustic events.

The cover 2630 is substantially disc-shaped and includes a bottomsurface 2634, a top surface 2636, and a sidewall 2638 extending from theperimeter of the base 2634 to the top surface 2636. According to someexemplary embodiments, the sidewall 2638 is planar, while in otherexemplary embodiments, the sidewall 2638 is non-planar. The bottomsurface 2634 is configured to be inserted within the top portion of thepressurizable chamber's sidewall 2616 and form a seal therewith. The topsurface 2636 is dimensioned the same as the bottom surface 2634according to some exemplary embodiments, while in other exemplaryembodiments, the top surface 2636 is dimensioned larger or smaller thanthe bottom surface 2634. According to some exemplary embodiments, atleast the bottom portion of the sidewall 2638 includes mating threads2639 for mating with the threads 2617. In other exemplary embodiments,the entire sidewall 2638 includes mating threads 2639. Although matingthreads 2639 are used in some exemplary embodiments to sealably couplethe top portion of the sidewall 2616 to the cover 2630, other methodsknown to people having ordinary skill in the art can be used, such asusing fasteners and using welds. The cover 2630 is fabricated fromsteel; however, according to other exemplary embodiments, the cover 2630is fabricated from any metal, metal alloy, polymer, wood, or othersuitable material known to people having ordinary skill in the art thatis capable of withstanding at least the second pressure (P₀) 2627, whichis described in further detail below.

The cover 2630 also includes an opening 2632 extending therethough. Theopening 2632 is substantially positioned centrally within the cover 2630and is sized to be the same diameter or shape as the opening 2681.However, opening 2632 can be sized and/or shaped differently thanopening 2681 according to other exemplary embodiments. According to theexemplary embodiment, at least a portion of the opening 2632 isvertically aligned with at least a portion of the opening 2681.

A first seal 2631 is positioned about the perimeter of the opening 2632and provides a pressure seal between the cover 2630 and the rock sample2680 about the opening 2632 and the opening 2681, thereby preventing orminimizing any second fluid 2626 leakage from the interface between theopening 2681 and the opening 2632. The first seal 2631 is shaped similarto the shape of the opening 2632. A second seal 2633 is positioned at alocation on the bottom surface 2634 which contacts the top surface 2682of the rock sample 2680. In some exemplary embodiments, the second seal2633 is positioned at a location on the bottom surface 2634 whichcontacts the perimeter of the top surface 2682 of the rock sample 2680.The second seal 2633 provides a pressure seal between the cover 2630 andthe rock sample 2680 substantially about the perimeter of the topsurface 2682 of the rock sample 2680, thereby preventing or minimizingany first fluid 2621 leakage from the interface between the cover 2630and the perimeter of the top surface 2682 of the rock sample 2680. Athird seal 2635 is positioned at the perimeter of the bottom surface2634 of the cover 2630. The third seal 2635 provides a pressure sealbetween the cover 2630 and the sidewall 2616 of the pressurizablechamber 2610, thereby preventing or minimizing any first fluid 2621leakage from the interface between the cover 2630 and the sidewall 2616of the pressurizable chamber 2610. The seals 2631, 2633, and 2635 are arubber gasket or any other suitable material known to people havingordinary skill in the art. Once the bottom portion of the cover 2630 isproperly inserted into the pressurizable chamber 2610, the first seal2631 and the second seal 2633 are in contact with the top surface 2682of the rock sample 2680. The pressure within the cavity 2612 surroundingthe rock sample 2680 is a first pressure (P₁) 2622 which can bedifferent than the second pressure 2627 within the openings 2632 and2681 during testing which is described in further detail below. Each ofthe first pressure 2622 and the second pressure 2627 is variable. Thus,a portion of the rock sample 2680 is exposed to the first pressure 2622while another portion of the rock sample 2680 is exposed to the secondpressure 2627 during testing.

Within the cavity 2612 surrounding the rock sample 2680, a first fluid2621 is placed. This portion of the cavity 2612 can be referred to as afirst chamber 2620. The first fluid 2621 fills up the first chamber 2620in some exemplary embodiments; however, in other exemplary embodiments,the first fluid 2621 fills a portion of the first chamber 2620. Thefirst fluid 2621 is water. However, other types of fluid having similarproperties can be used as the first fluid 2621 in other exemplaryembodiments. In some exemplary embodiments, the first fluid 2621includes sand particles or other similar particle types.

A second fluid 2626 flows into and fills up the opening 2681. Accordingto some exemplary embodiments, the second fluid 2626 is pumped intoopening 2632 and opening 2681. However, in other exemplary embodiments,the pressure of the second fluid is provided using other known methods,such as having a reservoir of second fluid fluidly coupled to theopenings 2632 and 2681 and having a piston (not shown) provide a forceto a movable plate (not shown) within the reservoir, similar to thesecond barrier 2540 described above. The opening 2681 can be referred toas a second chamber. The second fluid 2626 is water. However, othertypes of fluid having similar properties can be used as the second fluid2626 in other exemplary embodiments. In some exemplary embodiments, thesecond fluid 2626 includes sand particles or other similar particle

As the second pressure 2627 increases and the second fluid 2626 flowsinto the first chamber 2620 through the rock sample 2680, the firstpressure 2622 increases. To maintain the first pressure 2622 constant orsubstantially constant, a drain pipe 2595 is coupled to the interior ofthe first chamber 2620 and through the sidewall 2616 to allow the firstfluid 2621 and/or the second fluid 2626 that is present within the firstchamber 2620 to exit the first chamber 2620. The drain pipe 2595 isfabricated from a metal, metal alloy, polymer, or other suitablematerial capable of withstanding the first pressure 2622. In certainexemplary embodiments, the drain pipe pressure control valve 2597 isinstalled at a location along the drain pipe 2595 and is configured tobe opened and closed, either automatically or manually, to maintain thefirst pressure 2622 at a substantially constant pressure during thetesting process. In alternative exemplary embodiments, the drain pipe2595 is coupled to the interior of the first chamber 2620 through thebase 2614.

The operation of the acoustic emission testing system 2600 is describedwhile referring to FIG. 26. Once the acoustic emission testing system2600 is configured according to the description provided above, thedrain pipe control valve 2597 is set to maintain the pressure in thefirst chamber 2620 at the first pressure 2622. The first pressure 2622is determined to be the rock confining pressure, which is the pressureat which the rock sample 2680 was exposed to while in the wellbore. Thesecond fluid 2626 is pushed into the second chamber 2681 at the secondpressure 2627 which applies a force on the rock sample 2680 from within.The second pressure 2627 increases to a value above the first pressure2622 and is ramped up so that acoustic events, or cracking, occurs on orwithin the rock sample 2680. The second pressure 2627 is continuouslyramped up until the second pressure 2627 reaches a threshold pressure,where extensive acoustic events occur within the rock sample 2680. Oncethe second pressure 2627 increases above the first pressure 2622, thesecond fluid 2626 passes through the porous rock sample 2680 and entersinto the first chamber 2620. The first pressure 2622 would typicallyincrease due to the second fluid 2626 entering the first chamber 2620;however, the drain pipe control valve 2597 maintains the first pressure2622 substantially constant and allows the first fluid 2621 and/or thesecond fluid 2626 that has entered into the first chamber 2620 to exitthe first chamber 2620 through the pipe drain 2595. This thresholdpressure that is reached is the pressure that is to be generated in thewellbore for fracing the rock at that confining pressure. During thetesting procedure, the acoustic events are measured according to thedescriptions provided above. Additionally, the location of the acousticevents are determinable by people having ordinary skill in the arthaving the benefit of the present disclosure. Moreover, the direction inwhich the acoustic events are propagating also are determinable bypeople having ordinary skill in the art having the benefit of thepresent disclosure. The acoustic sensors 2570 obtain data when thesecond pressure 2627 is increased. Additionally, in some exemplaryembodiments, the acoustic sensors 2570 also obtain data when the secondpressure 2627 is decreased after reaching the threshold pressure.Although not illustrated, the first pressure 2622 and the secondpressure 2627 are monitored. According to some exemplary embodiments,the second pressure 2627 is recorded.

FIG. 27 shows an acoustic testing method 2700 in accordance with anexemplary embodiment. Although the acoustic testing method 2700illustrates one or more steps occurring in a certain order, one or moreof the steps occur in a different order according to other exemplaryembodiments. Additionally, one or more steps are combined into fewersteps according to some exemplary embodiments, while one or more stepsare expanded into more steps according to some exemplary embodiments.Thus, the illustrated order of steps and the number of steps are not tobe construed as being limiting.

The acoustic testing method 2700 includes a step 2710. At step 2710, arock sample is obtained from a wellbore at a certain depth and a rockconfining pressure exposed on the rock sample within the wellbore isobserved. According to some exemplary embodiments, the rock sample isobtained from the wellbore that is currently being drilled. In otherexemplary embodiments, the rock sample is obtained from a wellbore thatis nearby a site that is intended to be drilled. The method 2700 alsoincludes step 2715 where the rock sample is prepared so that the rocksample is insertable within a pressurizable chamber. The rock sample isfabricated into a desired shape so that it is insertable within thepressurizable chamber. Once the rock sample is prepared, the methodproceeds to step 2720 where the prepared rock sample is properly placedin the pressurizable chamber such that a first portion of the rocksample is exposable to a first chamber at a first pressure and a secondportion of the rock sample is exposable to a second chamber at a secondpressure. According to some exemplary embodiments, the first portionincludes at least a portion of the sidewall of the rock sample and thesecond portion includes the top surface of the rock sample. According tosome other exemplary embodiments, the first portion includes the topsurface of the rock sample and the second portion includes at least aportion of the sidewall of the rock sample. Yet, according to some otherexemplary embodiments, the first portion includes an exterior portion ofthe rock sample, such as the outer surface of the sidewall, and thesecond portion includes an interior portion of the rock sample. In analternative exemplary embodiment, the first portion includes an interiorportion of the rock sample and the second portion includes an exteriorportion of the rock sample, such as the outer surface of the sidewall.

The method 2700 also includes step 2725, where one or more acousticsensors are communicably coupled to the rock sample. According to someexemplary embodiments, three acoustic sensors are coupled to the surfaceof the rock sample in a manner where each acoustic sensor is positionedat a different elevation from one another. Although three acousticsensors are coupled to the rock sample, greater or fewer acousticsensors are usable in other exemplary embodiments. Also, although eachacoustic sensor is positioned at a different elevation from one another,at least one acoustic sensor is positionable substantially at the sameelevation as another acoustic sensor in other exemplary embodiments.Further, although the acoustic sensors are coupled to the surface of therock sample, one or more of the acoustic sensors are coupled to thepressurizable chamber in other exemplary embodiments.

The method 2700 also includes step 2730, where the first pressure in thefirst chamber is pressurized to at or substantially at the rockconfining pressure, which is the pressure that the rock sample wasexposed to while in the wellbore. According to some exemplaryembodiments, a first fluid that has been placed in the first chamberexerts the first pressure onto the first portion of the rock sample. Themethod 2700 also includes step 2735, where the second pressure in thesecond chamber is increased to a threshold pressure while the acousticevents occurring within the rock sample are recorded over time andspace. According to some exemplary embodiments, a second fluid, which isthe same or similar to the first fluid, has been placed in the secondchamber and exerts the second pressure onto the second portion of therock sample. The threshold pressure is the pressure at which acousticevents are formed quickly and extensively within and/or on the rocksample.

The method 2700 also includes step 2740. In step 2740, the fracturingevents that occurred over time and space are analyzed. This analysisincludes the processes described above according to some exemplaryembodiments. According to some exemplary embodiments, the intensity ofone or more fracturing events, or acoustic events, is determined.According to some exemplary embodiments, the location of one or morefracturing events, or acoustic events, that occurred within the rocksample is determined. According to some exemplary embodiments, thedirection in which one or more fracturing events, or acoustic events,are propagating is determined. After step 2740, the method 2700 proceedsto step 2745. In step 2745, at least one parameter of a high pressuredown hole fracturing program or at least one parameter of a down holedrilling program targeted to the sampled formation is determine basedupon the analysis of the fracturing events. For example, based upon theanalysis, the pressure that needs to be exerted by the bit on the rockwithin the wellbore to create a proper fracing program is the thresholdpressure, which is the pressure of the second pressure when substantialfracing of the rock occurs. In another example, the weight-on-bit iscalculable from knowing the pressure that the bit is to exert on therock within the wellbore.

FIG. 28 shows a cross-sectional view of an acoustic emission testingsystem 2800 in accordance with yet another exemplary embodiment of thepresent invention. Referring to FIG. 28, the acoustic emission testingsystem 2800 includes an acoustic emission testing device 2805communicably coupled to a data recorder 2809. The acoustic emissiontesting device 2805 includes a cutter holder 2810, the cutter 100, theindenter 550, an acoustic sensor holder 2850, an acoustic sensor 2870, afirst rod 2890, and a second rod 2895. Although the cutter 100 isdepicted in the exemplary embodiment, the rock sample 2300 (FIG. 23) orother type of hard or superhard component, replaces the cutter 100 inalternative exemplary embodiments.

The cutter holder 2810 includes a first surface 2812, a second surface2814, and a side surface 2816. The first surface 2812 is disposed in aplane that is substantially parallel to the plane that the secondsurface 2814 is disposed. The side surface 2816 extends from theperimeter of the first surface 2812 to the perimeter of the secondsurface 2814. According to some exemplary embodiments, the side surface2816 is substantially perpendicular to at least one of the first surface2812 and the second surface 2814. According to alternative exemplaryembodiments, the side surface 2816 is not substantially perpendicular toeither the first surface 2812 or the second surface 2814. The cutterholder 2810 is shaped in a substantially cylindrical shape, wherein thefirst surface 2812 is substantially circular shaped, the second surface2814 is substantially circular shaped, and the side surface 2816 issubstantially cylindrically and arcuately shaped. Although one exemplaryshape is provided for the cutter holder 2810, the cutter holder 2810 canbe shaped into any other geometric or non-geometric shape, such as asquare shaped cylinder or a triangular shaped cylinder, withoutdeparting from the scope and spirit of the exemplary embodiment. Thecutter holder 2810 is fabricated from steel; however, according to otherexemplary embodiments, the cutter holder 2810 is fabricated from anymetal, wood, or other suitable material known to people having ordinaryskill in the art that is capable of withstanding a load 2880, which isdescribed in further detail below. The load 2880 ranges from about zerokilonewtons to about seventy kilonewtons, but is higher in otherexemplary embodiments. In certain exemplary embodiments, the suitablematerial is capable of being machined or molded and is capable ofpropagating sound therethrough. In certain exemplary embodiments, thesuitable material is capable of propagating sound at a speed of about 1kilometers per second or higher.

The cutter holder 2810 also includes a first cavity 2820 and a secondcavity 2830 according to some exemplary embodiments. In certainexemplary embodiments, the cutter holder 2820 also includes a channel2838 extending from the first cavity 2820 to the second cavity 2830. Thefirst cavity 2820 is formed within the first surface 2812 of the cutterholder 2810 and extends toward the second surface 2814, but does notreach the second surface 2814. The first cavity 2820 includes a firstportion 2821 and a second portion 2825 formed adjacent to the firstportion 2821 according to certain exemplary embodiments. The firstportion 2821 extends from the first surface 2812 of the cutter holder2810 and extends into the cutter holder 2810 to the second portion 2825.According to some exemplary embodiments, the first portion 2821 isformed having a circular cross-section; however, the shape is differentin other exemplary embodiments. The first portion 2821 is sized toreceive at least a portion of the indenter 550, which has previouslybeen described. For example, the first portion 2821 is sized slightlylarger in diameter than the diameter of the indenter 550, therebyallowing the indenter 550 to easily and freely fit within the firstportion 2821.

The second portion 2825 extends from the first portion 2821 towards thesecond surface 2814. According to some exemplary embodiments, the secondportion 2825 is formed having a circular cross-section; however, theshape is different in other exemplary embodiments. The second portion2825 is sized to receive at least a portion of the cutter 100, which haspreviously been described, or some other hard or superhard material,such as the rock sample 2300 (FIG. 23), for which properties are to bedetermined. For example, the diameter of the second portion 2825 issized slightly larger in diameter than the diameter of the cutter 100,thereby allowing the cutter 100 to easily and freely fit within thesecond portion 2825. According to some exemplary embodiments, thecentral axial axis of the first portion 2821 is substantially the sameas the central axial axis of the second portion 2825; however, theseaxes are aligned differently in other exemplary embodiments. In someexemplary embodiments, the second portion 2825 has a smaller diameterthan the first portion 2821. In certain exemplary embodiments, the firstcavity 2820 includes the second portion 2825, but not the first portion2821. Thus, in these exemplary embodiments, the second portion 2825extends from the first surface 2812 towards the second surface 2814.

In certain exemplary embodiments, the second cavity 2830 is formedwithin the second surface 2814 of the cutter holder 2810 and extendstoward the second portion 2825 of the first cavity 2820, but does notreach the second portion 2825. However, this second cavity 2830 isoptional. A thickness 2835 is formed between the second portion 2825 andthe second cavity 2830. The thickness 2835 is able to withstand the load2880 without breaking. According to some exemplary embodiments, thesecond cavity 2830 is formed having a conicle cross-section; however,the shape is different in other exemplary embodiments. The second cavity2830 is sized to receive at least a portion of the acoustic sensor 2870,which is described in further detail below. In exemplary embodimentsthat do not include the second cavity 2830, the acoustic sensor 2870 ispositioned adjacent to the second surface 2814.

According to some exemplary embodiments, the channel 2838 is formedextending from the second cavity 2830 to the second portion 2825 of thefirst cavity 2820. The central axial axis of the channel 2838corresponds to the previously mentioned central axial axes according tocertain exemplary embodiments. The channel 2838 provides a directpathway for the acoustic waves to travel from the cutter 100 to theacoustic sensor 2870.

One or more of the cavities 2820, 2830, and channel 2838 are formed bymachining the cutter holder 2810 or molding the cutter holder 2810 tohave the cavities 2820, 2830 and the channel 2838 formed therein.Alternatively, one or more of the cavities 2820, 2830 and the channel2838 are formed using other methods or combination of methods known topeople having ordinary skill in the art. In certain exemplaryembodiments, the first cavity 2820 is formed in a manner to ensure thatthe cutter 100 is properly aligned in the same manner each time thecutter 100 is inserted within the first cavity 2820.

The cutter 100 has been previously described and is applicable to theexemplary embodiments. Briefly, the cutter 100 includes the substrate110 and the cutter table 120, which is formed or coupled to the top ofthe substrate 110. In the exemplary embodiment, the cutter table 120 isformed from PCD, but alternative exemplary embodiments have the cuttertable 120 fabricated from other materials, such as PCBN, withoutdeparting from the scope and spirit of the exemplary embodiment.Although cutter 100 has a planar cutter table 120, or is flat-faced, thecutter table 120 can be dome shaped, concave shaped, or any other shapeknown to people having ordinary skill in the art. As previouslymentioned, the cutter 100 includes finished and/or grounded cutters aswell as “raw” cutters.

The cutter 100 is inserted within the second portion 2825 of the firstcavity 2820. The cutter 100 is oriented within the second portion 2825so that the cutter table 120 is facing towards the first surface 2812,or away from the second surface 2814. According to some exemplaryembodiments, the entire cutter 100 is inserted within the second portion2825. However, in alternative exemplary embodiments, a portion of thecutter 100, which includes substantially the entire substrate 110, isinserted within the second portion 2825 of the first cavity 2820. Thus,in these alternative exemplary embodiments, at least a portion of thecutter table 120 is not inserted within the second portion 2825. Theportion of the cutter 100 inserted within the second portion 2825 issecurely positioned therein. However, according to some exemplaryembodiments, the portion of the cutter 100 inserted within the secondportion 2825 is loosely positioned therein. According to these otherexemplary embodiments, a lubricant (not shown) is disposed within thesecond portion 2825 between the cutter 100 and the surface of the secondportion 2825. Although the cutter 100 is described as being used in thisexemplary embodiment, other hard or superhard materials that desire atoughness testing can be used in lieu of the cutter 100.

The indenter 550 has been previously described and is not repeated forthe sake of brevity. The indenter 550 is sized to fit within at leastthe first portion 2821 of the first cavity 2820 so that it makes contactwith the cutter 100. In certain exemplary embodiments, the perimeter ofthe indenter 550 is sized substantially similar to the perimeter of thefirst portion 2821. However, in the exemplary embodiments where at leasta portion of the cutter table 120 is not within the first cavity 2820and is positioned elevationally above the first surface 2812, theindenter 550 can be dimensioned such that the perimeter of the indenter550 is greater than the perimeter of the first portion 2821 of the firstcavity 2820. The indenter 550 is oriented so that the indenter's firstend 650 makes contact with the cutter 100. Thus, in this embodiment,indenter 550 makes contact with the PDC layer, or cutter table 120, ofthe cutter 100. The load 2880 is applied to the indenter's second end652, which transmits the load 2880 onto the cutter 100.

The acoustic sensor holder 2850 includes a first surface 2852, a secondsurface 2854, and a side surface 2856. The first surface 2852 isdisposed in a plane that is substantially parallel to the plane that thesecond surface 2854 is disposed. The side surface 2856 extends from theperimeter of the first surface 2852 to the perimeter of the secondsurface 2854. According to some exemplary embodiments, the side surface2856 is substantially perpendicular to at least one of the first surface2852 and the second surface 2854. According to alternative exemplaryembodiments, the side surface 2856 is not substantially perpendicular toeither the first surface 2852 or the second surface 2854. The acousticsensor holder 2850 is shaped in a substantially cylindrical shape,wherein the first surface 2852 is substantially circular shaped, thesecond surface 2854 is substantially circular shaped, and the sidesurface 2856 is substantially cylindrically and arcuately shaped.Although one exemplary shape is provided for the acoustic sensor holder2850, the acoustic sensor holder 2850 is shaped differently in otherexemplary embodiments. The acoustic sensor holder 2850 is fabricatedfrom cemented carbide, such as cemented tungsten carbide; however,according to other exemplary embodiments, the acoustic sensor holder2850 is fabricated from any other suitable material, such as lead, thathas an acoustic impedance that is higher than the material used tofabricate the second rod 2895 and that is capable of withstanding theload 2880. In certain exemplary embodiments, the suitable material iscapable of being machined or molded and is capable of propagating sound.In certain exemplary embodiments, the suitable material is capable ofpropagating sound at a speed of about 1 kilometers per second or higher.The material that the acoustic sensor holder 2850 is fabricated has ahigher acoustic impedance than the material used to fabricate the secondrod 2895, which thereby causes the noise sound waves to be reflectedinto the second rod 2895 and not back into the acoustic sensor 2870.Hence, the signal to noise ratio that is detected by the acoustic sensor2870 is improved within the system 2800.

The acoustic sensor holder 2850 also includes a first cavity 2860 and asecond cavity 2868 according to some exemplary embodiments. The firstcavity 2860 is formed within the first surface 2852 of the acousticsensor holder 2850 and extends toward the second surface 2854, but doesnot reach the second surface 2854. The first cavity 2860 includes afirst portion 2861 and a second portion 2863 formed adjacent to thefirst portion 2861 according to certain exemplary embodiments. The firstportion 2861 extends from the first surface 2852 of the acoustic sensorholder 2850 to the second portion 2863 within the acoustic sensor holder2850. According to some exemplary embodiments, the first portion 2861 isformed having a circular cross-section; however, the shape is differentin other exemplary embodiments. The first portion 2861 is sized tosecurely receive a lower portion of the cutter holder 2810, whichincludes the cutter holder's second surface 2814. For example, the firstportion 2861 is sized slightly larger in diameter than the diameter ofthe cutter holder's second surface 2814, thereby allowing the cutterholder's second surface 2814 to easily and securely fit within the firstportion 2861.

The second portion 2863 extends from the first portion 2861 towards thesecond surface 2854. According to some exemplary embodiments, the secondportion 2863 is formed having a circular cross-section; however, theshape is different in other exemplary embodiments. The second portion2863 is sized to receive at least a portion of the acoustic sensor 2870.For example, the diameter of the second portion 2863 is sized largerthan the diameter of the acoustic sensor 2870. According to someexemplary embodiments, the central axial axis of the first portion 2861is substantially the same as the central axial axis of the secondportion 2863; however, these axes are aligned differently in some otherexemplary embodiments. In some exemplary embodiments, the second portion2863 has a smaller diameter than the first portion 2861.

In certain exemplary embodiments, the second cavity 2868 is formedwithin the second surface 2854 of the acoustic sensor holder 2850 andextends toward the second portion 2863 of the first cavity 2860, butdoes not reach the second portion 2863. However, this second cavity 2868is optional. A thickness 2869 is formed between the second portion 2863and the second cavity 2868. The thickness 2869 is able to withstand theload 2880 without breaking. According to some exemplary embodiments, thesecond cavity 2868 is formed having a circular cross-section; however,the shape is different in other exemplary embodiments. The second cavity2868 is sized to receive at least a portion of the second rod 2895,which is described in further detail below.

The cavities 2860, 2868 are formed by machining the acoustic sensorholder 2850 or molding the acoustic sensor holder 2850 to have thecavities 2860, 2868 formed therein. Alternatively, the cavities 2860,2868 are formed using other methods or combination of methods known topeople having ordinary skill in the art.

The acoustic sensor 2870 is a piezoelectric sensor in some exemplaryembodiments; however, the acoustic sensor 2870 is any other device typeknown to people having ordinary skill in the art, wherein the device iscapable of detecting acoustic transmissions. The acoustic sensor 2870detects elastic wave signals formed in the cutter 100, which thenconverts the elastic waves signal to a voltage signal so that the datacan be recorded and subsequently analyzed. The acoustic sensor 2870 hasa sensitivity range spanning from one to about 1,000 kilohertz, whichallows the detection of acoustic emission events too week or too shortto be detected based upon previously described system configurations.The acoustic sensor 2870 is positioned within at least the secondportion 2863 of the acoustic sensor holder's first cavity 2860. Incertain exemplary embodiments, a portion of the acoustic sensor 2870extends into the first portion 2861 of the acoustic sensor holder'sfirst cavity 2860. The acoustic sensor 2870 is coupled to or is incontact with the cutter holder 2850. In certain exemplary embodiments, aportion of the acoustic sensor 2870 is received within the second cavity2830 of the cutter holder 2810. In some exemplary embodiments, each ofthe indenter 550, the cutter 100, and the acoustic sensor 2870 aresubstantially aligned linearly. In certain exemplary embodiments, a lowdensity material 2875, such as a lubricant, is placed around theacoustic sensor 2870 once positioned within the acoustic sensor holder'sfirst cavity 2860. The low density material 2875 fills in the remainingportion of the first cavity 2860 between at least the surface of thefirst cavity's second portion 2863 and the acoustic sensor 2870. The lowdensity material 2875 isolates the acoustic sensor 2870 from detectingsurrounding environmental noise or at least reduces the detection ofthis noise. The acoustic sensor 2870 is communicably coupled to the datarecorder 2809 so that the voltage signal derived from the elastic wavesoccurring within the cutter 100 can be stored and subsequently analyzed.The acoustic sensor 2870 is coupled to the data recorder 2809 using acable 2808; however, according to other exemplary embodiments, theacoustic sensor 2870 is communicably coupled to the data recorder 2809wirelessly using wireless technology including, but not limited to,infrared and radio frequency. In the embodiments where the cable 2808couples the acoustic sensor 2870 to the data recorder 2809, a passageway2851 is formed extending from the acoustic sensor holder's side surface2856 to the acoustic sensor holder's first cavity 2860. The passageway2851 allows the cable 2808 to communicate from within the acousticsensor holder's first cavity 2860 to the data recorder 2809.

The first rod 2890 includes a first end 2891 that is oriented to applythe load 2880 onto the indenter's second end 652. The first rod's firstend 2891 is positioned

The second rod 2895 includes a first end 2896 that is shaped to besecurely coupled to the lower portion of the acoustic sensor holder2850. The first end 2896 includes a raised portion 2897 and a recessedportion 2898 surrounding the raised portion 2897. The raised portion2897 is shaped similarly to the shape of the acoustic sensor holder'ssecond cavity 2868 so that at least a portion of the raised portion 2897is insertable into the acoustic sensor holder's second cavity 2868 tosecurely couple the second rod 2895 to the acoustic sensor holder 2850.The raised portion 2897 includes a substantially planar surface 2899according to some exemplary embodiments; however, the surface 2899 isnon-planar depending upon the shape of the acoustic sensor holder'ssecond cavity 2868 in other exemplary embodiments. The second rod 2895is fabricated using steel, or alternatively, any other suitable materialcapable of withstanding the load 2880 and having a lower acousticimpedance than the material used to fabricate the acoustic sensor holder2850, such as aluminum, brass, plastic, and wood. As previouslymentioned, this low acoustic impedance material allows the sound tocontinue travelling into and through the material, rather than beingreflected back into the acoustic sensor 2870. In certain exemplaryembodiments, at least one of the cutter holder 2810, the acoustic sensorholder 2850, and the second rod 2895 is fabricated from a materialhaving a much higher density or a much lower density than at least oneof the other remaining components. For example, the density of one ofthe components is at least about 1.5 times greater than at least one ofthe previously mentioned components.

Although one exemplary configuration of the acoustic emission testingdevice 2805 has been illustrated and described, other configurations,known to people having ordinary skill in the art having the benefit ofthe present disclosure, can be used without departing from the scope andspirit of the exemplary embodiments. For example, the coupling and/orinterlocking features of adjacent components can be performed in avariety of ways in other exemplary embodiments. For example, the lowerportion of the cutter holder 2810 is partially inserted within a firstcavity 2860 formed in the upper portion of the acoustic sensor holder2850. Alternatively, in other exemplary embodiments, the upper portionof the acoustic sensor holder 2850 is partially inserted within a cavity(not shown) formed in the lower portion of the cutter holder 2810.

The data recorder 2809 is similar to the data recorder 590 (FIG. 5), butis capable of recording up to about 100,000 data points per second. Inalternative exemplary embodiments, the data recorder 2809 records evenmore data points per second. The data recorder 2809 records the datasent from the acoustic sensor 2870 and stores the data therein. In someexemplary embodiments, the data recorder 2890 also is communicablycoupled to one or more components, such as the first rod 2890, to obtaindata for quantifying the load 2880. The data is processed according tothe description provided above.

According to certain embodiments of the present invention, the conceptsdescribed above are included within an acoustic emission formationsampling tool, which is further described below. The acoustic emissionformation sampling tool is placed downhole into a wellbore and includesone or more indenters and one or more acoustic sensors acousticallycoupled to the indenters. The indenters are pushed into the adjacentrock formation within the wellbore with a load progressively increasingfrom a minimum load towards a maximum load, thereby causing cracks toform therein. The minimum load is about zero kilonewtons, while themaximum load is equal to the load that the drive mechanism, describedfurther below, is capable of producing. The cracking of the rockformation produces acoustic transmissions. The acoustic sensor detectsthese acoustic transmissions and provides a signal which is used todetermine one or more rock properties, such as CCS.

FIG. 29 shows a side schematic view of an acoustic emission formationsampling tool 2900 in an operating position 2902 within a wellbore 2908in accordance with another exemplary embodiment of the presentinvention. The acoustic emission formation sampling tool 2900 includes atool body 2910, one or more indenter guides 2920, one or more indenters2930, and one or more acoustic sensors 2870. In certain exemplaryembodiments; however, the indenter guides 2920 are optional. A rockformation 2906 radially surrounds the wellbore 2908.

The tool body 2910 is coupled, either directly or indirectly, to a drillstring (not shown) according to some exemplary embodiments, while inother exemplary embodiments, the tool body 2910 is suspended into thewellbore 2908 using one or more cables (not shown). The tool body 2910is cylindrically shaped and includes an outer surface 2912 which faces aborehole wall 2909 once the tool body 2910 is inserted into the wellbore2908. The outer surface 2912 forms at least one cavity 2914 therein,which extends inwardly into the tool body 2910. Although one cavity 2914is illustrated, there are several cavities 2914 formed within the outersurface 2912 in other exemplary embodiments. According to some examples,there are a plurality of cavities 2914, such as four cavities 2914,formed circumferentially and equidistantly apart around the outersurface 2912; however, one or more cavities 2914 are not formedequidistantly apart in other exemplary embodiments. In other examples,there are a plurality of cavities 2914 formed in vertical alignmentalong the outer surface 2912; however, in other examples, the cavities2914 are formed at different elevations along the outer surface 2912 andalso circumferentially around the perimeter of the outer surface 2912.

Each indenter guide 2920 is positionably aligned with a respectivecavity 2914 and is movable between a non-operating position (not shown),or retracted position, and the operating position 2902, or expandedposition. In certain exemplary embodiments, there are several indenterguides 2920 that are positionably aligned with a single cavity 2914.According to certain exemplary embodiments, the indenter guide 2920moves in a substantially perpendicular direction with respect to thelongitudinal length of the tool body 2910; however, one or more indenterguides 2920 move non-perpendicularly with respect to the longitudinallength of the tool body 2910. In the non-operating position, theindenter guide 2920 is positioned away from the borehole wall 2909 whenthe tool body 2910 is inserted into the wellbore 2908. In some examples,the indenter guide 2920 is positioned entirely within the cavity 2914when in the non-operating position. Conversely, in the operatingposition 2902, at least a portion of the indenter guide 2920 ispositioned in engagement with, adjacent to, or near, the borehole wall2909 when the tool body 2910 is inserted into the wellbore 2908.

The indenter guide 2920 includes a sidewall 2922 having a proximal end2923 and a distal end 2924 at an opposing end from the proximal end2923. The sidewall 2922 has a circular cross-sectional shape accordingto some exemplary embodiments; however, the cross-sectional shape of thesidewall 2922 is different in other exemplary embodiments. The sidewall2922 forms a channel 2925 extending from the distal end 2924 towards theproximal end 2923. In certain exemplary embodiments, there are severalchannels 2925 formed within the indenter guide 2920. In some exemplaryembodiments, the indenter guide 2920 also includes a flange 2921extending outwardly from the distal end 2924. According to someexemplary embodiments, the flange 2921 forms a portion of the outersurface 2912 of the tool body 2910 when the indenter guide 2920 is inthe non-operating position, or retracted position. According to someexemplary embodiments, a second flange (not shown) extends outwardlyfrom the proximal end 2923, thereby preventing the indenter guide 2920from inadvertently being decoupled from the tool body 2910. For example,the second flange stops the indenter guide 2920 from continuing to moveoutwardly from the tool body 2910 once the indenter guide 2920 is fullyextended. Although a second flange is used in some exemplary embodimentsto prevent the indenter guide 2920 from being decoupled from the toolbody 2910, other methods and devices known to persons having ordinaryskill in the art and having the benefit of the present disclosure, suchas a retaining ring, can be used to accomplish the same purpose withoutdeparting from the scope and spirit of the exemplary embodiments.

In certain exemplary embodiments utilizing more than one indenter guide2920, one or more of the indenter guides 2920 provide stability to thetool body 2910 when extended into the operating position 2902. Forexample, in the exemplary embodiments using two indenter guides 2920being separated 180 degrees apart, each of the indenter guides 2920 isbraced against opposing surfaces of the borehole wall 2909 when bothindenter guides 2920 are in the operating position 2902, which therebymaintains the tool body 2910 substantially along the center axis 2904 ofthe wellbore 2908. Although one indenter guide 2920 is illustrated,there are several indenter guides 2920 positioned along the outersurface 2912 of the tool body 2910 in other exemplary embodiments.According to some examples, there are a plurality of indenter guides2920, such as four indenter guides 2920, positioned circumferentiallyand equidistantly apart around the outer surface 2912; however, one ormore indenter guides 2920 are not positioned equidistantly apart fromanother indenter guide in other exemplary embodiments. In otherexamples, there are a plurality of indenter guides 2920 positioned invertical alignment along the outer surface 2912; however, in otherexamples, the indenter guides 2920 are positioned at differentelevations along the outer surface 2912 and also circumferentiallyaround the perimeter of the outer surface 2912.

The indenter guide 2920 is positioned from the non-operating position tothe operating position 2902 and back to the non-operating position usinga drive mechanism (not shown). The drive mechanism used for moving theindenter guide 2920 is within the purview of persons having ordinaryskill in the art and having the benefit of the present disclosure. Forexample, the drive mechanism is a hydraulic mechanism according to someexemplary embodiments. However, in alternative exemplary embodiments,the drive mechanism is an electric mechanism, such as a motor, or apneumatic mechanism. Exemplary drive mechanisms used in performingsimilar type operations in a downhole tool, which include under reamers,expandable stabilizers, and side wall coring units, are described inU.S. Pat. No. 4,354,558, entitled “Apparatus and Method for Drillinginto the Sidewall of a Drill Hole,” and issued to Jageler et al. on Oct.19, 1982; U.S. Pat. No. 4,629,011, entitled “Method and Apparatus forTaking Core Samples from a Subterranean Well Side Wall,” and issued toReinhardt on Dec. 16, 1986; U.S. Pat. No. 4,714,119, entitled “Apparatusfor Hard Rock Sidewall Coring a Borehole,” and issued to Hebert et al.on Dec. 22, 1987; U.S. Pat. No. 5,617,927, entitled “Sidewall RotaryCoring Tool,” and issued to Maissa on Apr. 8, 1997; U.S. Pat. No.7,493,971, entitled “Concentric Expandable Reamer and Method,” andissued to Nevlud et al. on Feb. 24, 2009; and U.S. Pat. No. 7,900,717,entitled “Expandable Reamers for Earth Boring Applications,” and issuedto Radford et al. on Mar. 8, 2011. Although drive mechanisms used withindownhole tools for coring applications and expanding reamer applicationsare applicable to the present drive mechanism, other drive mechanismsused within other downhole tools may also be applicable as a method ordevice for moving the indenter guide 2920 without departing from thescope and spirit of the exemplary embodiments.

Each indenter 2930 is positioned within the channel 2925 of a respectiveindenter guide 2920 and is movable between a non-operating position (notshown) and the operating position 2902 within the indenter guide 2920.Thus, in certain embodiments where several channels 2925 are formedwithin the indenter guide 2920, a plurality of indenters 2930 arepositioned within a single indenter guide 2920. According to certainexemplary embodiments, the indenter 2930 moves in a substantiallyperpendicular direction with respect to the longitudinal length of thetool body 2910. However, according to other exemplary embodiments, theindenter 2930 moves in a substantially non-perpendicular direction withrespect to the longitudinal length of the tool body 2910. In thenon-operating position, the indenter 2930 is positioned away from theborehole wall 2909 when the tool body 2910 is inserted into the wellbore2908. In some examples, the indenter 2930 is positioned entirely withinthe cavity 2914 when in the non-operating position. Conversely, in theoperating position 2902, at least a portion of the indenter 2930 is inengagement with the borehole wall 2909 and is exerting a force onto theborehole wall 2909. Thus, a portion of the indenter 2930 is extendablebeyond the distal end 2924 of the indenter guide's sidewall 2922.

The indenter 2930 is similar to indenter 550 (FIG. 5) according to someexemplary embodiments. Indenter 2930 includes a body 2932 and a contactend 2934 coupled to the body 2932. The body 2932 is cylindrically shapedaccording to some exemplary embodiments, while in other exemplaryembodiments, the body 2932 is shaped differently. The body 2932 includesa bottom end 2933 located opposite the contact end 2934. According tosome exemplary embodiments, the body 2932 forms a passageway 2931extending from the bottom end 2933 towards the contact end 2934, whichis explained further below. The contact end 2934 is conicle-shaped andhas a first end 2935 and a second end 2936 positioned opposite the firstend 2935. The second end 2936 is coupled to the body 2932. The first end2935 is substantially planar, but is shaped differently, such asdome-shaped, in other exemplary embodiments. According to some exemplaryembodiments, the contact end 2934 is fabricated using hard or superhardmaterials, such as polycrystalline diamond compact, and the body 2932 isfabricated using cemented tungsten carbide. However, the contact end2934 and the body 2932 are fabricated using other known suitablematerials, which can be the same material or different materials, thatcan crack the surrounding rock formation 2906 without itself cracking.

The indenter 2930 is positioned from the non-operating position to theoperating position 2902 and back to the non-operating position using adrive mechanism (not shown). The drive mechanism used for moving theindenter 2930 is within the purview of persons having ordinary skill inthe art and having the benefit of the present disclosure. The drivemechanism used for moving the indenter 2930 is the same as the drivemechanism used for moving the indenter guide 2920 in some exemplaryembodiments. In other exemplary embodiments, the drive mechanism usedfor moving the indenter 2930 is different than the drive mechanism usedfor moving the indenter guide 2920. In other exemplary embodiments, thedrive mechanism used for moving the indenter 2930 operates inconjunction with the operation of the drive mechanism used for movingthe indenter guide 2920.

One or more seal rings 2940 are positioned circumferentially around thebody 2932 of the indenter 2930 and provide a seal between the indenter2930 and the indenter guide 2920. Thus, fluid and/or other contaminantspresent within the wellbore 2908 do no enter the tool body 2910 throughmovement of the indenter 2930 and the indenter guide 2920. The sealrings 2940 are fabricated using a suitable material known to personshaving ordinary skill in the art, such as an elastomer, a metal, or ametal alloy. A groove (not shown) is present in either of the body 2932of the indenter 2930 or the sidewall 2922 of the indenter guide 2920.Thus, in some exemplary embodiments, one of either the indenter 2930 orthe indenter guide 2920 is stationary with respect to the seal ring2940.

The acoustic sensor 2870 is a piezoelectric sensor in some exemplaryembodiments; however, the acoustic sensor 2870 is any other device typeknown to people having ordinary skill in the art, wherein the device iscapable of detecting acoustic transmissions. The acoustic sensor 2870detects acoustic transmissions formed in the adjacent rock formation2906 when the indenter 2930 is pushed into the adjacent rock formation2906 and cracks the adjacent rock formation 2906. The acoustic sensor2870 converts the acoustic transmissions to a voltage signal, or othertype of signal, so that the information can be recorded and subsequentlyanalyzed pursuant to the descriptions previously provided. In certainexemplary embodiments, the signal from the acoustic sensor 2870 is sentto the surface of the wellbore 2808, either using a cable 2972 orwirelessly, so that the signal is analyzed. The acoustic sensor 2870 hasa sensitivity range spanning from one to about 1,000 kilohertz. Incertain exemplary embodiments, at least a portion of the acoustic sensor2870 is positioned within the passageway 2931 of the indenter 2930 sothat it is positioned closer to the cracks occurring in the adjacentrock formation 2906. However, in other exemplary embodiments, theacoustic sensor 2870 is positioned adjacent to, or near, the bottom end2933 of the indenter 2930. In certain exemplary embodiments, theacoustic sensor 2870 is surrounded by a lubricant (not shown), similarto that described above. Although one type of acoustic sensor 2870 isdescribed, alternative embodiments include other types of acousticsensors capable of detecting cracks being initiated and propagatedwithin the adjacent rock formation 2906.

The acoustic emission formation sampling tool 2900 is operated by beinglowered into a wellbore 2908. The acoustic emission formation samplingtool 2900 is coupled to a drill string (not shown) in some exemplaryembodiments; while in others, the acoustic emission formation samplingtool 2900 is lowered into the wellbore 2908 using one or more cables(not shown). In the exemplary embodiments where the acoustic emissionformation sampling tool 2900 is coupled to the drill string, theacoustic emission formation sampling tool 2900 rotates along with therotation of the drill string. Once positioned at a desired depth withinthe wellbore 2908 for which properties of surrounding rock formations2906 are to be determined, the acoustic emission formation sampling tool2900 stops rotating, if it was rotating. The drive mechanism pushes oneor more indenters 2930, and the one or more indenter guides 2920according to some exemplary embodiments, into the surrounding rockformation 2906 at a minimum load. The drive mechanism pushing theindenter 2930 and the indenter guide 2920 is the same in some exemplaryembodiments, while different in other exemplary embodiments. Also, oneor more indenters 2930 operate simultaneously in certain exemplaryembodiments, while in other exemplary embodiments, one or more indenters2930 operate independently from one another at a different time. Thedrive mechanism increases the load that the indenter 2930 applies ontothe surrounding rock formation 2906 over time until the drive mechanismreaches a maximum load that causes the indenter 2930 to exert thismaximum load onto the surrounding rock formation 2906. Once the drivemechanism achieves the maximum load, the drive mechanism causes theindenter 2930, and the indenter guide 2930 according to some exemplaryembodiments, to retract into the acoustic emission formation samplingtool 2900. The indenter 2930 causes the surrounding rock formation toinitiate cracking at some intermediate load between the minimum load andthe maximum load. This cracking generates acoustic transmissions whichare received by the acoustic sensor 2870, which in turn transmits asignal to the surface. The signal is analyzed pursuant to thedescriptions provided above, thereby determining one or more properties,including the CCS, of the rock formation at the desired depth within thewellbore 2908. Additionally, the values of the load that is applied tothe rock formation 2906 is monitored, and optionally recorded.

It is expected that the indenter 2930 is capable of applying theappropriate loads onto the adjacent rock formations 2906 many timesbefore being replaced or repaired due to damage. This repeated use ofthe indenter 2930 allows the operator to perform several tests withinthe same wellbore 2908 at various desired depth locations in thewellbore 2908. The acoustic emission formation sampling tool 2900,thereby, allows the operator to determine at least the confinedcompressive strength of the surrounding rock formation 2906 along thewellbore 2908 in situ.

FIG. 30 shows a top schematic view of an acoustic emission formationsampling tool 3000 in an operating position 3002 within a wellbore 2908in accordance with another exemplary embodiment of the presentinvention. Referring to FIG. 30, the acoustic emission formationsampling tool 3000 includes a tool body 3010, a plurality of indenterguides 3020, a plurality of indenters 2930, and a plurality of acousticsensors 2870. The acoustic emission formation sampling tool 3000 issimilar to the acoustic emission formation sampling tool 2900 (FIG. 29)and includes additional components than those previously mentioned, suchas one or more drive mechanisms. However, acoustic emission formationsampling tool 3000 is dissimilar to the acoustic emission formationsampling tool 2900 (FIG. 29) in that there are four indenter guides3020A, 3020B, 3020C, and 3020D, four corresponding indenters 2930A,2930B, 2930C, and 2930D, and four corresponding acoustic sensors 2870A,2870B, 2870C, and 2870D that are each positioned radially andequidistantly around the tool body 3010. Each indenter guide 3020 issimilar to the indenter guide 2920 (FIG. 29). However, each indenterguide 3020 includes a flange 3021 that extends outwardly from a distalend 3024 of the indenter guide 3020. Each flange 3021 extends outwardlyand arcuately to form about one-fourth of an outer surface 3012 of thetool body 3010 when the indenter guide 3020 is in a non-operatingposition, or retracted position. According to some exemplaryembodiments, a first indenter guide 3020A, a second indenter guide3020B, a third indenter guide 3020C, and a fourth indenter guide 3020Dare positioned into the operating position 3002 at about the same time.The operating position 3002 is the position at which the indenter guide3020 and/or the indenter 2930 is in engagement with the borehole wall2909 of the borehole 2908. Thus, the indenter guides 3020 providestability to the acoustic emission formation sampling tool 3000 whenpositioned in the operating position 2908. According to some of theseexemplary embodiments, one of a first indenter 2930A, a second indenter2930B, a third indenter 2930C, and a fourth indenter 2930D exerts a loadonto the surrounding rock formation 2906 together with at least oneother indenter 2930A, 2930B, 2930C, and 2930D. According to some otherof these exemplary embodiments, each one of the first indenter 2930A,the second indenter 2930B, the third indenter 2930C, and the fourthindenter 2930D exerts a load onto the surrounding rock formation 2906independently and at a different non-overlapping time period than any ofthe other indenters 2930A, 2930B, 2930C, and 2930D even though each ofthe indenter guides 3020A, 3020B, 3020C, and 3020D are in the operableposition 3002. In alternative exemplary embodiments, indenter guides3020A, 3020B, 3020C, and 3020D separated by about 180 degrees arepositioned into the operating position 3002 at about the same time,thereby providing the stability to the acoustic emission formationsampling tool 3000. For example, the first and third indenter guides3020A and 3020C are positioned into the operating position 3002 at aboutthe same time, while second and fourth indenter guides 3020B and 3020Dare positioned into the operating position 3002 at about the same timebut at a different time period than the first and third indenter guides3020A and 3020C. By performing the loading in a differentnon-overlapping time period, the cracks propagated by a loaded indenter2930A can also be sensed and/or recorded by the sensors 2870B, 2870C,2870D of one or more non-loaded indenters 2930B, 2930C, 2930D. The timelapse between the crack initiation sensed by the sensor 2870A in theloaded indenter 2930A and the crack initiation sensed by one or moreunloaded sensors 2870B, 2870C, 2870D can provide a direct measurement ofthe density of the rock being sampled.

Each of the other components of the acoustic emission formation samplingtool 3000, whether mentioned above or not, such as the drive mechanism,is similar to the components of the acoustic emission formation samplingtool 2900 (FIG. 29), and therefore is not duplicatively described hereinagain for the sake of brevity. The acoustic emission formation samplingtool 3000 also operates in a similar manner as the operation of theacoustic emission formation sampling tool 2900 (FIG. 29) and istherefore not repeated again for the sake of brevity. The modificationsapplicable to the acoustic emission formation sampling tool 2900 (FIG.29) also apply to the acoustic emission formation sampling tool 3000.For example, although four indenter guides 3020 are shown in the currentexemplary embodiments, the number of indenter guides is greater or fewerin other exemplary embodiments. In one example, there are three indenterguides equidistantly and circumferentially separated by about 120degrees.

FIG. 31 shows a side schematic view of an acoustic emission formationsampling tool 3100 in an operating position 3102 within a wellbore 2908in accordance with another exemplary embodiment of the presentinvention. Referring to FIG. 31, the acoustic emission formationsampling tool 3100 includes a tool body 3110, a plurality of indenters2930, a plurality of acoustic sensors 2870, and a pressure arm 3150. Theacoustic emission formation sampling tool 3100 is similar to theacoustic emission formation sampling tool 2900 (FIG. 29) and includesadditional components than those previously mentioned, such as one ormore drive mechanisms described above. However, in certain exemplaryembodiments, the acoustic emission formation sampling tool 3100 does notinclude the optional indenter guide (not shown).

The tool body 3110 is coupled, either directly or indirectly, to a drillstring (not shown) according to some exemplary embodiments, while inother exemplary embodiments, the tool body 3110 is suspended into thewellbore 2908 using one or more cables (not shown). The tool body 3110is cylindrically shaped and includes an outer surface 3112 which faces aborehole wall 2909 once the tool body 3110 is inserted into the wellbore2908. The outer surface 3112 forms a plurality of cavities 3114 therein,which are arranged in a vertical and substantially linear array along atleast a portion of the longitudinal length of the tool body 3110. Eachcavity 3114 extends inwardly into the tool body 3110. Although fourcavities 3114 are illustrated, there are greater or fewer cavities 3114formed within the outer surface 3112 in other exemplary embodiments.Although one arrangement of the cavities 3114 is provided, thearrangement is different in other exemplary embodiments.

Each of the indenters 2930 are similar to the indenter 550 (FIG. 5)according to some exemplary embodiments. Each indenter 2930 ispositioned within a respective cavity 3114 and is movable between anon-operating position (not shown) and the operating position 3102. Inthe operating position 3102, the indenter 2930 is at least partiallypositioned within the cavity 3114 and is pushing into the adjacent rockformation 2906 to exert a load onto the rock formation 2906. Conversely,in the non-operating position, the indenter 2930 is not pushing into theadjacent rock formation 2906. In certain exemplary embodiments, theindenter 2930 is entirely positioned within the corresponding cavity3114. According to certain exemplary embodiments, the indenter 2930moves in a substantially perpendicular direction with respect to thelongitudinal length of the tool body 3110. However, according to otherexemplary embodiments, the indenter 2930 moves in a substantiallynon-perpendicular direction with respect to the longitudinal length ofthe tool body 3110.

Each indenter 2930 is positioned from the non-operating position to theoperating position 3102 and back to the non-operating position using adrive mechanism (not shown). The drive mechanism used for moving theindenter 2930 is within the purview of persons having ordinary skill inthe art and having the benefit of the present disclosure. The drivemechanism used for moving one indenter 2930 is the same as the drivemechanism used for moving all the indenters 2930 in some exemplaryembodiments. In other exemplary embodiments, the drive mechanism usedfor moving one indenter 2930 is different than the drive mechanism usedfor moving one or more of the remaining indenters 2930.

Although not illustrated, one or more seal rings (not shown), similar tothe seal rings 2940 (FIG. 29), are positioned circumferentially aroundthe indenter 2930 to provide a seal between the indenter 2930 and theportion of the tool body 3110 which defines the cavity 3114 according tocertain exemplary embodiments. Thus, fluid and/or other contaminantspresent within the wellbore 2908 do no enter the tool body 3110 throughmovement of the indenter 2930 within the cavity 3114. The seal ringoperates in a similar manner as described above.

The acoustic sensors 2870 are a piezoelectric sensor in some exemplaryembodiments; however, the acoustic sensors 2870 are any other devicetype known to people having ordinary skill in the art, wherein thedevice is capable of detecting acoustic transmissions. The acousticsensors 2870 detect acoustic transmissions formed in the adjacent rockformation 2906 when the indenter 2930 is pushed into the adjacent rockformation 2906 and cracks the adjacent rock formation 2906. The acousticsensors 2870 convert the acoustic transmissions to a voltage signal, orother type of signal, so that the information can be recorded andsubsequently analyzed pursuant to the descriptions previously provided.In certain exemplary embodiments, the signal from the acoustic sensors2870 are sent to the surface of the wellbore 2908, either using a cable(not shown) or wirelessly, so that the signal is analyzed. The acousticsensors 2870 have a sensitivity range spanning from one to about 1,000kilohertz in certain exemplary embodiments. The acoustic sensors 2870are positioned adjacent to the indenter 2930 in the manners aspreviously mentioned. In certain exemplary embodiments, the acousticsensors 2870 are surrounded by a lubricant (not shown), similar to thatdescribed above. Although one type of acoustic sensor 2870 is described,alternative embodiments include other types of acoustic sensors capableof detecting cracks being initiated and propagated within the adjacentrock formation 2906.

The pressure arm 3150 is coupled to the tool body 3110 using a pivot pin3152. The pressure arm 3150 is hydraulically operated to pivot aroundthe pivot pin 3152 and move away from the tool body 3110 to positionitself in an operating position 3103. The pressure arm 3150 ispositioned to pivot away from the tool body 3150 in a direction that isopposite to the direction in which the cavities 3114, and hence also theindenters 2930, are facing. When desired, the pressure arm 3150 ishydraulically operated to pivot around the pivot pin 3152 and movetowards the tool body 3110 to position itself in a non-operatingposition (not shown). This hydraulic operation is known to personshaving ordinary skill in the art and is described in detail within U.S.Pat. No. 4,354,558, entitled “Apparatus and Drilling Method for Drillinginto the Sidewall of a Drill Hole, and issued to Jageler et al. on Oct.19, 1982, which has been incorporated by reference herein.Alternatively, other methods, such as an electric motor, is used to movethe pressure arm 3150 in other exemplary embodiments. Although thepressure arm 3150 is described and illustrated, any other device capableof engaging and anchoring itself to a surface of the wellbore wall 2909can be used in other exemplary embodiments.

The acoustic emission formation sampling tool 3100 is operated by beinglowered into the wellbore 2908. The acoustic emission formation samplingtool 3100 is coupled to a drill string (not shown) in some exemplaryembodiments; while in others, the acoustic emission formation samplingtool 3100 is lowered into the wellbore 2908 using one or more cables(not shown). In the exemplary embodiments where the acoustic emissionformation sampling tool 3100 is coupled to the drill string, theacoustic emission formation sampling tool 3100 rotates along with therotation of the drill string. Once positioned at a desired depth withinthe wellbore 2908 for which properties of surrounding rock formations2906 are to be determined, the acoustic emission formation sampling tool3100 stops rotating, if it was rotating. Once positioned at the desireddepth, the pressure arm 3150 is pivoted around the pivot pin 3152 toengage with a surface 3108 of the wellbore wall 2909. The pressure arm3150 continues to move away from the tool body 3110 causing the toolbody 3110 to move toward an opposite surface 3109 of the wellbore wall2909 until the tool body 3110 engages with the opposite surface 3109.The tool body 3150 is moved downward, either by applying a downwardforce or by allowing gravity to act upon the tool body 3110, therebycausing the pressure arm 3150 to dig into the surface 3108 of thewellbore wall 2909 and further anchor the tool body 3110 to the wellborewall 2909.

Once the tool body 3110 is in contact with the opposite surface 3109 ofthe wellbore wall 2909, the drive mechanism pushes one or more indenters2930 into the surrounding rock formation 2906 at a minimum load. One ormore indenters 2930 operate simultaneously in certain exemplaryembodiments, while in other exemplary embodiments, one or more indenters2930 operate independently from one another at different times. Thedrive mechanism increases the load that the indenter 2930 applies ontothe surrounding rock formation 2906 over time until the drive mechanismreaches a maximum load that causes the indenter 2930 to exert thismaximum load onto the surrounding rock formation 2906. Once the drivemechanism achieves the maximum load, the drive mechanism causes theindenter 2930 to retract into the acoustic emission formation samplingtool 3100. The indenter 2930 causes the surrounding rock formation 2906to initiate cracking at some intermediate load between the minimum loadand the maximum load. This cracking generates acoustic transmissionswhich are received by the acoustic sensor 2870, which in turn transmitsa signal to the surface. At loads above the intermediate load, thecracking continues to propagate through the rock formation 2906 andfurther generate additional acoustic transmissions. The signal from theacoustic sensor 2870 is analyzed pursuant to the descriptions providedabove, thereby determining one or more properties, including the CCS, ofthe rock formation 2906 at the desired depth within the wellbore 2908.Additionally, the values of the load that is applied to the rockformation 2906 is monitored, and optionally recorded. Once the test hasbeen completed, the tool body 3110 is raised to dislodge the pressurearm 3150 from the surface 3108 of the wellbore wall 2909 and then thepressure arm 3150 is pivotally moved into the non-operating position.The acoustic emission formation sampling tool 3100 is then moved to adifferent elevation within the wellbore 2908.

The positioning of the indenters 2930 within the acoustic emissionformation sampling tool 3100 allows for variations within acoustictransmissions to occur over a vertical section of the wellbore 2908 whenperforming tests with the acoustic emission formation sampling tool 3100being at a constant position within the wellbore 2908. Also, it isexpected that the indenter 2930 is capable of applying the appropriateloads onto the adjacent rock formations 2906 many times before beingreplaced or repaired due to damage. This repeated use of the indenter2930 allows the operator to perform several tests within the samewellbore 2908 at various desired depth locations in the wellbore 2908.The acoustic emission formation sampling tool 3100, thereby, allows theoperator to determine at least the confined compressive strength of thesurrounding rock formation 2906 along the wellbore 2908 in situ.

Although the indenters 2930 and the acoustic sensors 2870 are describedas being installed within acoustic emission formation sampling tools2900, 3000, and 3100, the indenters 2930 and the acoustic sensors 2870can be used within other types of downhole tools, such as reamers,centralizers, and drill bits, without departing from the scope andspirit of the exemplary embodiment. Additionally, although the indenters2930 are installed within the downhole tool to provide a load onto thewellbore sidewall 2909, the indenters 2930 can be installed within thedownhole tool to provide a load onto the bottom of the wellbore 2908.For example, the indenters 2930 is installed within the face of a bit incertain exemplary embodiments.

FIG. 32 illustrates a flowchart of a method 3200 for determining one ormore properties of a rock formation located within a wellbore using theacoustic emission formation sampling tool in accordance with anexemplary embodiment of the present invention. Although certain stepsare shown as proceeding in a particular order, the sequence of steps canbe varied without departing from the scope and spirit of the exemplaryembodiment. Also, although certain functions are performed in one ormore steps, the number of steps for performing that function can beincreased or decreased without departing from the scope and spirit ofthe exemplary embodiment.

Referring to FIG. 32, at step 3205, the method 3200 starts. From step3205, method 3200 proceeds to step 3210. At step 3210, an acousticformation sampling tool, similar to any of the described embodimentsabove, is positioned within a wellbore at a depth of interest. Uponcompletion of step 3210, method 3200 proceeds to step 3220. At step3220, at least one indenter of the acoustic formation sampling tool isengaged to a portion of a rock formation surrounding at least a portionof the wellbore. Upon completion of step 3220, method 3200 proceeds tostep 3230. At step 3230, one or more cracks are created in the rockformation when a load is exerted onto the indenter. The cracks form oneor more acoustic events. Upon completion of step 3230, method 3200proceeds to step 3240. At step 3240, a sensor senses the acoustic eventsthat formed as the indenter is loaded into the rock formation. Uponcompletion of step 3240, method 3200 proceeds to step 3250. At step3250, one or more properties of the rock formation is determined fromthe acoustic events. Upon completion of step 3250, method 3200 proceedsto step 3260. At step 3260, the determined rock property of the rockformation is provided as an input into one or more of a hydraulicfracturing program, a perforation program, a drilling program, a linerprogram, or a completion program. Each of these program types an use ofthese program types are known to persons having ordinary skill in theart having the benefit of the present disclose and therefore is notdescribed for the sake of brevity. After step 3260, method 3200 proceedsto step 3265 where method 3200 is stopped.

Although each exemplary embodiment has been described in detail, it isto be construed that any features and modifications that are applicableto one embodiment are also applicable to the other embodiments.Furthermore, although the invention has been described with reference tospecific embodiments, these descriptions are not meant to be construedin a limiting sense. Various modifications of the disclosed embodiments,as well as alternative embodiments of the invention will become apparentto persons of ordinary skill in the art upon reference to thedescription of the exemplary embodiments. It should be appreciated bythose of ordinary skill in the art that the conception and the specificembodiments disclosed may be readily utilized as a basis for modifyingor designing other structures or methods for carrying out the samepurposes of the invention. It should also be realized by those ofordinary skill in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims. It is therefore, contemplated that the claims willcover any such modifications or embodiments that fall within the scopeof the invention.

1. A downhole tool, comprising: a tool body comprising an outer surfacedefining one or more cavities therein, the cavity extending into thetool body; one or more indenters, each indenter positioned within acorresponding cavity, each indenter positionable into an operatingposition and a non-operating position; and one or more acoustic sensorspositioned within the cavity and adjacent to the indenter, wherein theindenter is positioned at least partially beyond the outer surface whenin the operating position, and wherein the acoustic sensor senses one ormore acoustic events occurring when the indenter is in the operatingposition.
 2. The downhole tool of claim 1, wherein the tool bodycomprises a substantially longitudinal cylindrical shape and wherein theindenters move substantially perpendicularly with respect to the lengthof the tool body.
 3. The downhole tool of claim 1, wherein one or moreof the indenters comprise a contact end coupled to a body, at least aportion of the contact end being positioned beyond the outer surfacewhen the indenter is in the operating position.
 4. The downhole tool ofclaim 3, wherein the contact end comprises polycrystalline diamondcompact.
 5. The downhole tool of claim 3, wherein the body comprises abottom end, the bottom end defining an opening extending inwardlytowards the contact end, and wherein at least a portion of the acousticsensor is positioned within the opening.
 6. The downhole tool of claim1, wherein the indenters are positioned circumferentially around thetool body.
 7. The downhole tool of claim 1, wherein the indenters arealigned vertically in a substantially linear array along the tool body.8. The downhole tool of claim 1, further comprising a pressure armpivotally coupled to the tool body, the pressure arm pivotally movingaway from the tool body in a direction opposite from the indenters. 9.The downhole tool of claim 1, further comprising one or more indenterguides that form a channel therein, at least a portion of each indenterguide positioned within the cavity, the indenter guide positionablebetween a second operating position and a second non-operating position,the indenter guide extending away from the tool body when in the secondoperating position, and wherein the indenter is positioned within thechannel of the indenter guide.
 10. The downhole tool of claim 9, whereineach indenter guide is positioned at the second operating position atthe same time.
 11. A downhole acoustic emission testing system,comprising: a drill string extending into a wellbore surrounded by arock formation; and a downhole tool coupled to the drill string andpositioned within the wellbore, the downhole tool, comprising: a toolbody comprising an outer surface defining one or more cavities therein,the cavity extending into the tool body; one or more indenters, eachindenter positioned within a corresponding cavity, each indenterpositionable into an operating position and a non-operating position;and one or more acoustic sensors positioned within the cavity andadjacent to the indenter, wherein the indenter is applying a load ontothe rock formation when in the operating position, the load rangingbetween a minimum load and a maximum load, and wherein the acousticsensor senses one or more acoustic events occurring within the rockformation when the indenter is in the operating position.
 12. Thedownhole acoustic emission testing system of claim 11, wherein theacoustic sensor receives the acoustic events and transmits one or moresignals corresponding to each acoustic event.
 13. The downhole acousticemission testing system of claim 11, wherein the tool body comprises asubstantially longitudinal cylindrical shape and wherein the indentersmove substantially perpendicularly with respect to the length of thetool body.
 14. The downhole acoustic emission testing system of claim11, wherein at least a portion of the indenter comprises polycrystallinediamond compact.
 15. The downhole acoustic emission testing system ofclaim 11, wherein the indenters are positioned circumferentially aroundthe tool body.
 16. The downhole acoustic emission testing system ofclaim 11, wherein the indenters are aligned vertically in asubstantially linear array along the tool body.
 17. The downholeacoustic emission testing system of claim 11, wherein the downhole toolfurther comprises a pressure arm pivotally coupled to the tool body, thepressure arm pivotally moving away from the tool body in a directionopposite from the positioning of the indenters.
 18. The downholeacoustic emission testing system of claim 11, wherein the downhole toolfurther comprises one or more indenter guides that form a channeltherein, at least a portion of each indenter guide positioned within thecavity, the indenter guide positionable between a second operatingposition and a second non-operating position, the indenter guideextending away from the tool body when in the second operating position,and wherein the indenter is positioned within the channel of theindenter guide.
 19. A method for testing a rock formation surrounding awellbore, comprising: inserting a downhole tool into a wellboresurrounded by a rock formation, the downhole tool, comprising: a toolbody comprising an outer surface defining one or more cavities therein,the cavity extending into the tool body; one or more indenters, eachindenter movably positioned at least partially within a correspondingcavity, each indenter positionable into an operating position and anon-operating position; and one or more acoustic sensors positionedwithin the cavity and adjacent to the indenter, positioning one or moreindenters in contact with the rock formation; applying a load onto theindenter thereby supplying the load onto the rock formation; generatingone or more acoustic events within the rock formation; and detecting theone or more acoustic events.
 20. The method of claim 19, wherein theload ranges from a minimum load to a maximum load, the loadprogressively increasing over time.
 21. The method of claim 19, whereinthe tool body comprises a substantially longitudinal cylindrical shapeand wherein the indenters move substantially perpendicularly withrespect to the length of the tool body.
 22. The method of claim 19,wherein the indenters are positioned circumferentially around the toolbody.
 23. The method of claim 19, wherein the indenters are alignedvertically in a substantially linear array along the tool body.
 24. Themethod of claim 19, wherein positioning one or more indenters in contactwith the rock formation comprises moving the tool body adjacent to therock formation.
 25. The method of claim 19, wherein positioning one ormore indenters in contact with the rock formation comprises moving atleast a portion of the outer surface of the tool body that forms thecavity adjacent to the rock formation.
 26. The method of claim 19,further comprising determining the confined compressive strength of therock formation exposed to the indenter from the one or more acousticevents without removing the downhole tool from the wellbore.
 27. Themethod of claim 19, further comprising determining one or moreproperties of the rock formation without removing the downhole tool fromthe wellbore and inputting the one or more properties of the rockformation into one or more of a hydraulic fracturing program, aperforation program, a drilling program, a liner design, and acompletion program.